David Davis's ex-aide James Chapman to launch anti-Brexit party

James Chapman, also a former Daily Mail political editor, says: "I did my best to make Brexit work for a year - and it won't."

James Chapman and David Davis
Image: James Chapman (left) is former chief of staff to Brexit Secretary David Davis
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The Brexit Secretary's former chief of staff has confirmed he will launch a new political party to put the brakes on Britain's departure from the EU.

James Chapman, a key aide to David Davis until earlier this year, revealed he will formally announce the creation of "the Democrats" during an anti-Brexit march in central London on 9 September.

Since quitting Mr Davis's Department for Exiting the EU (DExEU) before June's snap general election, Mr Chapman has become an outspoken critic of the Government's Brexit strategy.

Having spent Tuesday posting a series of derogatory Twitter messages about his former boss, Mr Chapman said in a statement: "I did my best to make Brexit work for a year - and it won't.

"There is no upside and it is clear that every sector of our economy will suffer for decades to come. Project Fear is Project Fact.

"The first duty of our politicians is to stand up for the interests of their constituents - and that means sound money and job opportunities for all."

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Davis: We want 'slick' EU customs arrangements

He added: "The MPs that have left Britain careering towards a cliff worse than Black Wednesday have failed in that duty and are guilty of misconduct in public office.

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"The march on Parliament will be for members of all parties and none - but I will be announcing my intention to lead a new party, the Democrats, which will reverse Brexit with no second referendum.

"It's time for all of those with consciences to put nation before country and make sure we are Great Britain once again - not the Little Britain of Nigel Farage and Vladimir Putin's wet dreams."

The People's March for Europe will end outside the Houses of Parliament next month, with the event being held under the tagline "unite, rethink, reject Brexit now".

George Osborne, David Cameron and James Chapman
Image: The former Daily Mail political editor (right) went on to work for George Osborne

Mr Chapman was former political editor of the Daily Mail and is now a partner at public relations firm Bell Pottinger.

He was a key architect of the Treasury's so-called Project Fear during the EU referendum campaign, in his previous role as ex-chancellor George Osborne's press chief.

As Mr Davis presented the Government's new paper on post-Brexit customs arrangements on Tuesday, Mr Chapman accused the Brexit Secretary of only working a three-day week - among a string of allegations he made about the Cabinet minister.

Asked to comment on Mr Chapman's criticism, Mr 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."

A DExEU source said Mr Davis "works full-time negotiating our exit from the EU, as well as fulfilling his duties to Parliament as a Cabinet minister and an MP".