Philip Hammond used forecasts he knew were inaccurate to undermine the government's Brexit stance, David Davis claimed today.
The former Brexit secretary accused Mr Hammond of hampering negotiations by turning dubious predictions about the impact of no deal into 'weapons'.
Speaking on the fringes of the Tory conference, Mr Davis said it drove him 'mad' when the Chancellor would start raising problems at crucial points in the EU exit talks.
He said Mr Hammond 'was using a forecast which internally the reports said was inaccurate and did not reflect the future' when preparations were being made for a no-deal outcome.
'Internally, that was the briefing going on inside,' he added.
'So these are not forecasts, they are weapons.'
Mr Davis said he was looking forward to being a backbencher during Treasury questions in the Commons.
'My first question to the Chancellor will be could he please name one forecast by the Treasury, or the OBR (Office for Budget Responsibility) or the Bank of England from the last 50 years that was right?'
Mr Davis said there would be 'immediate harm' on all sides if Britain left the bloc without a deal.
But he said it would be resolved swiftly and criticised Mr Hammond for raising doubts.
He said: 'It used to drive me mad sometimes when Government ministers, I'll name no names but you can make a very easy guess, he's been on the air today, we'd get to a negotiation point and suddenly somebody over here would start saying, 'Oh, we are in a terrible problem here, we can't do this, we can't do that, we are in difficulty, all these companies are going to leave the country'.
'No they are not.'
He added: 'We shouldn't frighten ourselves to death.'
Mr Davis, a TA SAS veteran, said he was told on an interrogation course during his training that the 'only thing that will defeat you on this is your own imagination'.
'That's a real risk with this, we frighten ourselves to death when in fact we can make practical arrangements,' he added.
'There will be immediate harm on all sides but the difficulties for us will be shortish term and mostly resolved in a matter of months,' he said.