Brexit minister Steve Baker apologised on Thursday after telling MPs he heard claims that Treasury civil servants had deliberately drawn up negative economic assessments to try and steer Government policy.

After the comments, the Tory MP was accused of undermining the integrity of the civil service.

The storm erupted after Jacob Rees-Mogg asked the minister 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."

Baker said that account was "essentially correct."

"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," he added.

Grant strongly denied the claims, and Baker was forced into an apology when an audio recording emerged which contradicted the minister's recollection of the comments.

Downing Street, which had initially said there was no reason to question Baker's version of events, insisted the minister had made a "genuine mistake" after the tape was released by Prospect magazine.

"This was a genuine mistake, he has apologised to Charles Grant, and will clarify his remarks in the House. We consider the matter closed," said a Number 10 source.

After audio emerged, Baker tweeted: "This morning in Parliament, I answered a question based on my honest recollection of a conversation.

"As I said, I considered what I had understood to be implausible, because of the impartiality of the civil service.

"The audio of that conversation is now available and I am glad the record stands corrected. In the context of that audio, I accept that I should have corrected the premise of the question.

"I will apologise to Charles Grant, who is an honest and trustworthy man. As I have put on record many times, I have the highest regard for our hard working civil servants. I will clarify my remarks to the House."

Rees-Mogg said of Grant: "If he says he didn't make it, he says he didn't make it, but he made a very similar claim on Twitter."

Asked if civil servants were deliberately skewering evidence, Rees-Mogg delivered a swipe at Chancellor Philip Hammond, telling a Mile End Institute event: "I think the blame should always lie with ministers actually.

"We knew very clearly before the Brexit vote that the Treasury was being guided very strongly by the then-Chancellor of the Exchequer, and it is the Chancellor of the Exchequer who has to take responsibility for his department."

The minister's Commons claims had provoked a furious backlash from the union representing senior civil servants, which accused Baker of being irresponsible and "cowardly" for failing to challenge the "conspiracy theory".

Earlier this week, Baker came under similar fire for dismissing Whitehall forecasts as "always wrong."