British Secretary of State for Exiting the European Union (Brexit Minister) David Davis | Ben Stansall/AFP via Getty Images Former aide accuses Brexit secretary David Davis of being lazy and a liar James Chapman also encouraged his former colleagues at the Brexit department to resign rather than ‘facilitate misconduct in public office.’

Brexit Secretary David Davis has been accused by his former chief of staff of being lazy, incompetent and a liar.

James Chapman, who served as senior aide to Davis until before the general election in June, accused his former boss of "working three days a week," and encouraged his former colleagues at the Brexit department to resign rather than "facilitate misconduct in public office."

He lashed out at his former boss in a series of tweets, after the Brexit secretary described him as a Remainer in a TV interview Monday.

Apparently in response to the interview, Chapman tweeted that both Davis and British Prime Minister Theresa May “don’t have the first idea what they are doing” in the Brexit negotiations.

The ex-aide accused his former boss of telling "a lie" in a tweet from May in which the Brexit secretary said that trade deals with non-EU countries could remain in place after Brexit, although Chapman did suggest it may have been because Davis did not read his ministerial briefings on the subject.

In another tweet he apologized to the Slovakian Prime Minister for an incident in which Davis allegedly said "if you think we are going to pay so you can sell us your cars, forget it" and for the fact that the meeting lasted "only one hour as [David Davis] wanted to go home."

When asked about the allegations on Sky News, Davis said: "James was a Remainer from the beginning, but he was a very good chief of staff. I am not going to criticize or argue with him [on air]."

A Whitehall official said Davis worked “very hard” and "full time.” “He is an MP, cabinet member and negotiating Britain’s exit from the EU,” the official added.

Last week Chapman, who was previously political editor of the Daily Mail, called Brexit a "catastrophe" and encouraged Remain-leaning MPs to come together in a new party.