Downing Street has defended a minister whose Commons exchange with an MP sparked a row about the independence of the civil service.
Unions accused Brexit Minister Steve Baker of failing to challenge a “half-baked conspiracy theory” that Treasury officials were trying to influence policy to stay in the EU customs union.
Number 10 said Mr Baker had made clear he found the allegation “implausible”.
It was put forward in a question by backbench Tory MP Jacob Rees-Mogg.
During Commons Brexit questions, Mr Rees-Mogg asked Mr Baker to confirm if he had heard from Charles Grant, of the Centre for European Reform think tank, that “officials in the Treasury have deliberately developed a model to show that all options other than staying in the customs union were bad and that officials intended to use this to influence policy”.
In response, Mr Baker said he was “sorry to say” that Mr Rees-Mogg’s account was “essentially correct”, adding: “At the time I considered it implausible because my direct experience is that civil servants are extraordinarily careful to uphold the impartiality of the civil service.”
Mr Baker was challenged by Opposition MPs as he delivered his answer to Mr Rees-Mogg, prompting him to add: “I didn’t say it was correct. I said the account that was put to me is correct.
“It was put to me, I considered it an extraordinary allegation, I still consider it an extraordinary allegation.”
Mr Grant then released a statement denying the account of what he had said.
He said he recalled telling Mr Baker at an event at the Conservative Party conference that he was aware of Treasury research showing the economic costs of leaving the customs union outweighed the benefits of striking free trade deals.
But he added: “I did not say or imply that the Treasury had deliberately developed a model to show that all non-customs union options were bad, with the intention to influence policy.”
Conservative MP Antoinette Sandbach said she had been at the event and had not heard comments as reported by Mr Rees-Mogg, a prominent Brexiteer on the Tory benches.
Dave Penman, general secretary of the FDA union which represents senior civil servants, criticised Mr Baker’s response to the question.
“To stand at the despatch box and refuse to challenge a half-baked conspiracy theory about the civil service – one that is even now being disowned by its supposed source – is the height of irresponsibility from a serving minister,” he said.
“It is not good enough for Mr Baker to simply shrug his shoulders and allow unfounded accusations about officials to go unchallenged.”
Earlier this week the union clashed with Mr Baker after the minister dismissed a leaked government report about the economic impact of Brexit, saying civil service forecasts were “always wrong”.
Downing Street said a senior Number 10 aide had spoken to Mr Baker about the remarks, and that the prime minister had full confidence in him.
A spokesman for the PM added: “The minister has set out the events as he recalls them. We have got no reason to question his account. This relates to a private conversation which took place some time ago.”