Government rift over Brexit assessments: Now Tories turn on the Treasury

The drama started when his fellow Brexiteer Jacob Rees-Mogg asked Mr Baker to confirm that he had been told by Charles Grant, of the Centre for European Reform, 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”.

Mr Rees-Mogg added: “If this is correct, does he share my view that it goes against the spirit of the Northcote-Trevelyan reforms that underpin our independent civil service?” He was referring to a landmark 1854 report that established the independence and impartiality of the civil service. 

Mr Baker replied: “I am sorry to say that my honourable friend’s account is essentially correct.” Brexit Secretary David Davis then winced in dismay. 

Mr Baker said: “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. I think we must proceed with great caution in this matter but I heard him raise this issue. 

“I think we need to be very careful not to take this forward in an inappropriate way. But he has reminded me of something which I heard. I think it would be quite extraordinary if it turned out that such a thing had happened.”