Theresa May and Boris Johnson exchanged furious blows today as a tumultuous Tory conference kicked off.
The former foreign secretary launched another vicious attack on the PM's Chequers plan for Brexit - branding it 'deranged' and 'preposterous'.
In one bruising jibe, Mr Johnson pointed out that she was a Remainer during the referendum two years ago - whereas he is a true believer in the project.
And he urged the government to back ambitious projects like building a bridge between Northern Ireland and Scotland.
But a defiant Mrs May shot back that her critics were 'playing politics' and insisted she is 'not bluffing' about driving a hard bargain with the EU.
Speaking during an interview on the BBC's Andrew Marr Show to kick off Tory conference, Mrs May said: 'I do believe in Brexit.'
Scottish Tory leader Ruth Davidson also took aim at Mr Johnson, pointing out that he had stayed as a senior member of the government during the Brexit negotiations.
The bitter clashes came as Conservatives gathered in Birmingham for a conference that is set to be dominated by Brexit and questions about Mrs May's future.
The premier is facing a desperate struggle to hang on as leader amid grass roots fury about her 'soft' approach to cutting ties with the EU, and jostling by leadership rivals.
The Prime Minister had hoped to show that her Government is about more than just Brexit by using her party conference to announce new policies.
These include plans to crack down on foreigners buying homes and proposals for a nationwide festival in 2022 - the year of the next scheduled General Election.
But once again Mr Johnson ensured the focus is still on his own leadership credentials by giving a long interview in The Sunday Times attacking Mrs May's policies.
In a direct swipe at her over Brexit, he said: 'Unlike the Prime Minister, I campaigned for Brexit.'
Mr Johnson - who is only coming to Birmingham for one fringe event on Tuesday - branded Mrs May's Chequers plan 'entirely preposterous'.
PM presents Scots Tory leader Ruth Davidson with gifts for baby
Theresa May presented pregnant Scottish Tory leader Ruth Davidson with a Downing Street baby grow last night.
Mrs May and Ms Davidson met to discuss Brexit and other key issues after arriving at the party's conference in Birmingham.
But despite the high-stakes battle going on with Eurosceptics and the EU, the PM had found time to stock up on some gifts.
Ms Davidson is less than five weeks away from giving birth to her first child, and has joked that she is the size of a 'naval frigate'.
She tweeted a video of herself with Mrs May after being handed a No10 branded baby grow, teddy bear and a copy the PM's favourite book, Swallows and Amazons.
The book, written in the 1930s, involves two competiting child families playing on an island in the Lake District.
Ms Davidson said: 'Had a pre #CPC18 meeting with @Theresa_May to discuss all things conference/Brexit/budget.
'Didn't expect to be surprised with a gift for the wee one at the end (including the PM's favourite book, Swallows & Amazons, for when they're older).'
The blueprint would involve the UK effectively staying in the single market for goods, and collecting some tax on behalf of the EU.
Mrs May says it is the only way of keeping smooth trade and ensuring there is no hard Irish border.
But Brexiteers are demanding a looser Canada-style arrangement that would make it easier to strike trade deals elsewhere in the world.
Suggesting he may be able to strike a better deal than Mrs May, he told the newspaper: 'Unlike the Prime Minister, I fought for this, I believe in it, I think it's the right thing for our country and I think that what is happening now is, alas, not what people were promised in 2016.'
He also accused Mrs May of misleading him and other ministers over the 'backstop' plan agreed with the EU regarding Northern Ireland last December.
The EU says the backstop means Northern Ireland should stay in a customs partnership with the EU.
He said: 'I remember going in to see the PM and her advisers and being absolutely reassured that this was just a form of words that was necessary to float the negotiations off the rocks.
'What has happened is that the issue has been allowed to dominate in a way that we were expressly promised would not happen.'
Mr Johnson insists that he voiced his concerns to Number Ten - but was ignored.
He said: 'I repeatedly erupted to try to get my point across in public in a way that was deemed at the time to be unhelpful, and that was nothing compared to what went on in private.'
Despite giving a round of explosive interviews which have overshadowed Tory party conference, he insisted that he is not disloyal and just wants Chequers to be dropped rather than the PM to be ousted.
He said: 'I am like a loyal and faithful Labrador that is relentlessly returning to her an object that she has mistakenly chucked away in the form of her own first instincts about how to do this.'
And he gave a distinctly cool response when asked if Mrs May should stay on as leader and fight the next election.
He said: 'The Prime Minister said she is going to serve for as long as her party wants her, and I certainly think she should.'
May defends hostile environment immigration policies despite Windrush scandal
Theresa May today defended her 'hostile environment' immigration policies despite the Windrush scandal.
The PM was confronted on the BBC's Andrew Marr show about those who lost their jobs and homes after being caught up in the scandal.
She apologised that some long-standing UK residents of Caribbean origin had been caught by her Immigration Act.
But she refused to apologise for the policy itself.
Mrs May told BBC1's Andrew Marr Show: 'The point of the policy was to ensure that those people who were here in the UK illegally were identified and that appropriate action was taken.
'What went wrong was that people from the Windrush generation who were here legally, who had every right to be here, who had helped to build our great national institutions, found themselves unable to show that through documentation and got caught up in that.
'I think for most people, they do want to know that the Government is taking action against those people who come to this country illegally or stay in this country illegally.
'What we need to do is make sure that in doing that, we don't find people who have every right to be here being caught up in it. That's what went wrong.'
She added: 'I apologise for the fact that some people who should not have been caught up in that were caught up in that, with, in some cases, tragic results.'
Mrs May was asked how many people from the Windrush generation had lost their homes, their jobs and their benefits or been refused NHS treatment as a result of her hostile environment policy.
She did not provide any figures but told Andrew Marr: 'What we have been doing is looking at every aspect of the impact on people from the Windrush generation.
'These people are British. We have apologised for what happened to these people. This should never have happened to people.
'It is right that we are making every effort to ensure that we can give people, not just the right papers, but the confidence and the reassurance of knowing that what they always felt and knew, and that what everybody else always felt and knew, is not in question. They are part of us.'
Setting out an alternative policy platform as the Conservative Party conference began in Birmingham, the former cabinet minister said the UK should build a bridge to Ireland and put the HS2 rail line on hold to focus on a high-speed link in the north of England.
And he urged a more 'Tory' domestic platform to combat the threat from left-wing Labour under Jeremy Corbyn.
'I think we need to make the case for markets,' he said.
'I don't think we should caper insincerely on socialist territory. You can't beat Corbyn by becoming Corbyn.'
A Cabinet ally of Mrs May played down the intervention, telling MailOnline that Mr Johnson does not have enough support among Tory MPs to oust the PM.
They said: 'It is not that damaging to have stories like this in the papers today.
'He is making a lot of noise, but Boris does not have the numbers in the parliamentary party, and he knows that is the case.
'There is a big contrast between the respectful stance David Davis has taken, arguing his case, and the way Boris has pursued his own personal ambitions.'
But Mrs May hit back at the criticisms in an interview with Marr today - insisting that her Chequers plan is the only credible proposal on the table.
She told Marr: 'What I have said to the EU is very clear. They have said they have some concerns with the proposals we have put together.
'Let's hear what the details of those concerns. If they have counter proposals, let's hear what those counter proposals are.
'What is clear is what we have put forward is in the national interest and we did it because what the EU was offering us was unacceptable.'
She said that 'at the heart of Chequers is a free trade deal, and she hit back at calls for Britain to have a Canada style trade deal with the EU instead.
She said: 'Canada for the UK is not on the table from the EU. What's on the table is a basic free trade agreement for Great Britain with Northern Ireland remaining in the customs union, remaining in the single market.'
The PM had earlier given her own interview with The Sunday Times to insist she is going nowhere as leader.
Signalling that she intended to remain in Number 10 for years to come, she said: 'There's a long-term job to do.'
She added: 'It's not just about Brexit, it's about the domestic agenda as well.
'I think we're at a very important and historic moment for the UK.
'There are real opportunities for the UK outside the European Union.'
Setting out her plans for a festival in post-Brexit Britain, she said: 'We want to showcase what makes our country great today.
'We want to capture that spirit for a new generation, celebrate our nation's diversity and talent, and mark this moment of national renewal with a once-in-a-generation celebration.'
Mrs May also told the Sun on Sunday that she was 'not bluffing' when she said 'no deal is better than a bad deal' when it comes to leaving the EU.
'I believe that we can get a deal,' she added. 'I believe we can get a good deal and that's what we are working for. But nobody should be in any doubt.'
Boost for May as poll finds 64% of Tories want MPs to back her Brexit deal
Theresa May received a much-needed boost today as a poll revealed that 64 per cent of Tory voters want MPs to back her Brexit plans.
The PM is facing a revolt from her own MPs and activists over her under-fire Chequers deal, while EU leaders have also ruled it out.
Boris Johnson has launched a fresh broadside against her Brexit plans branding them 'deranged'.
But a poll by GQRR found that most Tory voters want MPs to support Mrs May in whatever deal she gets from Brussels.
It found that 64 per cent of Tory voters want MPs to back whatever divorce deal May is able to strike with Brussels, rather than vote it down.
It also found that if the PM's deal is rejected by MPs then 58 per cent of Tories want her to be given more time to get a deal.
And she continues to outpoll her rival Jeremy Corbyn, the survey found.
The poll, published in Politico, revealed that 37 per cent said they feel 'warm' to her, compared to just 33 per cent for the Labour leader.
The findings came from a survey of 1,477 adults.
Mrs May took aim at Tories such as Mr Johnson stirring up the situation, saying they needed to 'put the country first'.
'My message to the Conservative Party is going to be that people voted to leave the EU,' she said.
'I believe it's a matter of trust in politicians that we deliver on that vote for people. We're the party that always puts country first and puts the national interest first. And that's what I want us to be doing.
'The only proposal on the table at the moment that delivers that is the Chequers plan.'
But she is facing an explosive few days at Tory Party conference as she has to face her party activists who are seething at her Chequers plan.
And former Brexit Secretary David Davis piled on the pressure today as he also took aim at the government's Brexit strategy, urging a more 'robust approach'.
'The tendency on the part of the Whitehall advice, and the No 10 advice in particular, is to say, what's negotiable, what's achievable,' Mr Davis told The Sunday Telegraph.
'That's not the way you design your policies. You design your policies, then sell them, then amend them if you do have to do that but not the other way around.'
He added: 'What would you like me to pay you?' is not the right approach to a negotiation. I massively simplify, but that's the equivalent.'
Tory chairman Brandon Lewis stopped short of condemning Mr Johnson for his 'deranged' jibe, saying 'Boris has his own style of using language'.
But he told BBC News: 'I think the party is focused around being behind the prime minister to deliver a good deal for the United Kingdom as we leave the European Union.
'You would have to ask Boris what he thinks of the language he's using.'
Under plans to hit property buyers from abroad, people and businesses who do not pay tax in Britain will face a surcharge of between 1 per cent and 3 per cent when they buy a property, with the money funding measures to tackle rough sleeping.
The conference got off to a rough start yesterday when an embarrassing security gaffe in the official app allowed access to the contact details of Cabinet ministers and senior MPs.
Tory chairman Brandon Lewis apologised for the breach of security and the UK's data watchdog said it would make enquiries about the case.
Activists and journalists heading to the conference discovered the major security problem in the official app which many use to keep track of events.
Mr Lewis said the 'technical issue' had been resolved but 'we are investigating the issue further and apologise for any concern caused'.
The Information Commissioner's Office said it would be 'making enquiries with the Conservative Party' and 'organisations have a legal duty to keep personal data safe and secure'.
The profiles of former foreign secretary Mr Johnson and Environment Secretary Michael Gove were among those reportedly accessed.