Jeremy Corbyn is facing calls to block the selection of an 'anti-Semitic' candidate as Labour's hopeful to unseat Boris Johnson.
The Labour leader was urged to intervene to prevent local party members picking Ali Milani for the coveted job of fighting Mr Johnson in his Uxbridge seat.
The row erupted after Mr Milani won through to the shortlist for the Labour nomination despite a record of anti-Semitic remarks made when he was a teenager.
Mr Milani, a vice-president of the National Union of Students, has previously sparked outrage by saying 'Israel has no right to exist'.
He has also allegedly suggested Jewish people are mean, with a tweeted reply in 2012 that read: 'Nah, you won't mate. It'll cost u a pound. #jew.'
Last night, campaign group Labour Against Antisemitism called on Mr Corbyn to intervene to block Mr Milani.
Spokesman Euan Philipps said: 'It is outrageous that a person such as Mr Milani could be selected to stand as a Labour parliamentary candidate when his appalling behaviour is on public record. He has a well-documented history of publicly making offensive comments that draw on classic anti-Semitic tropes to abuse and discriminate against Jews.'
Labour activists have become increasingly confident that Mr Corbyn's popularity in London puts Mr Johnson's 5,034 majority in Uxbridge and South Ruislip within reach at the next Election.
But some critics in the party were yesterday appalled to learn that the favourite to win the Labour nomination was Mr Milani.
They seized on remarks widely reported last year where he challenged the state of Israel's right to exist. In 2013, he said: 'I want to be the President of Israel. They have a self-destruct button, right?'
Last night, Labour made it clear it would not intervene, stressing that Mr Milani had previously apologised for his comments. Mr Milani said: 'I have and always will unreservedly apologise for the comments I made as a teenager.'
Corbynite teacher: Every sane human is an anti-Semite
by Martin Beckford for the Mail on Sunday
A fervent supporter of Jeremy Corbyn has been kicked out of the teaching profession for declaring 'every sane human is anti-Semitic'.
Harpreet Singh ranted on Facebook that Israel should be 'wiped off the planet' and 'of course we hate Jews'. Of the Labour leader he wrote: 'God bless Jeremy Corbyn. He is a modern day saint. And I mean it. If one of your loved ones was at the mercy of Israel, you would feel his morality, his conviction & his commitment to The Truth.'
The 48-year-old, a former head of maths at Sandye Place Academy in Bedfordshire, was suspended from his job after colleagues reported him. He was banned from teaching anywhere in England by the Teaching Regulation Agency after being found guilty of unacceptable professional conduct over the 'offensive/racist comments'.