A former aide to David Davis has launched an outspoken attack on his old boss, claiming the Brexit Secretary only worked "a three-day week".

James Chapman, who worked at the Department for Exiting the European Union[DExEU] after the referendum last year, has become a ferocious critic of Brexit and has called for the formation of a new centrist party to fight for Britain's future in the bloc.

As Mr Davis gave a series of media interviews on temporary customs arrangements, Mr Chapman fired off numerous tweets claiming his former boss had been "working 3 day week since day one" and had Nigel Farage, the former Ukip leader, on speed dial.

He also criticised Mr Davis over comments about Labour’s Diane Abbott, the Shadow Home Secretary, referring to an encounter where the Secretary of State had to apologise for remarks made about her in private text messages after the vote to trigger Article 50.

Asked what he made of Mr Chapman's recent suggestion that the Brexit department was "in chaos", Mr Davis said: "James when he came to me was...a Remainer; we knew that. But he did a good job; he was a good chief of staff. I'm not going to criticise him. I just don't do that, I'm afraid."

Asked if he had Mr Farage on speed dial, Mr Davis told LBC Radio: "Not on speed dial, I've got his number somewhere, I haven't used it for, Lord knows, since I was last on your programme with him.”

He added: "So what? All this stuff, this is the small change of politics."

When asked about Mr Chapman’s comments, a DExEU spokeswoman simply repeated Mr Davis’s comments but a departmental source later noted: “The Secretary of State works full time negotiating our exit from the European Union as well as fulfilling his duties to Parliament as a Cabinet minister and an MP."