LONDON – David Davis, the UK Brexit Secretary, has been subjected to a string of vicious personal attacks by his former chief of staff, who has claimed that he is so incompetent he can neither work a mobile phone nor make a ham sandwich.

James Chapman, who used to be Davis’ right-hand man in the Department for Exiting the European Union (DExEU), attacked the work ethic and credibility of his former boss in a series of tweets on Tuesday morning.

It came as Davis toured TV studios to promote the government’s Brexit strategy, which was fleshed out today with new documentation on the customs union.

Chapman said that Davis only works three days a week, is rude to European heads of state and is so incompetent that those around him are guilty of facilitating misconduct in public office.

Here are the tweets in question.

He said Davis only works three days a week:

That he can't make a sandwich:

That he's lying to the public and never reads his "red box" briefing papers:

https://twitter.com/jameschappers/status/897378339098431488

That he can't work out how to save a phone number by himself so makes his staff do it:

;...and that he sometimes phones up the EU's chief negotiator by mistake:

https://twitter.com/jameschappers/status/897345646826573825

That he takes six sugars in his tea, and makes somebody else stir it:

https://twitter.com/jameschappers/status/897381982635741184

That he insulted the Prime Minister of Slovakia:

https://twitter.com/jameschappers/status/897353398986711040

Chapman has emerged in the past week as a stridently pro-Remain voice on Twitter, posting a string of messages suggesting a new pro-EU political party while on holiday with his wife in Greece.

It is a stark reversal from his previous career, which saw him spend around 13 years as a journalist for the fiercely eurosceptic Daily Mail newspaper, where he was political editor.

While in the job, he advanced their editorial line with articles under headlines like "Liars, turncoats and cowards!", which attacked supporters of Jean-Claude Juncker, now president of the European Commission, whom he called a "euro-fanatic."

James Chapman liars turncoats and cowards

Foto: source Daily Mail

Others include "YES, PRIME MINISTER!", celebrating David Cameron's decision to call the referendum, "Le stitch-up", which rankled at increased UK payments to the EU, and an attack on EU free movement rules headlined "THERE ARE TOO MANY MIGRANTS."

James Chapman too many migrants

Foto: source Daily Mail/Business Insider

He left journalism for 2015 to work for then-Chancellor George Osborne and subsequently for Davis at DExEU.

When asked about the tweets in an interview with 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 criticise or argue with him [on air]."

DExEU declined to comment on Chapman's claims.