Richard Tice, co-chairman of Brexit campaign group Leave Means Leave, said reported conflict within Government was now affecting the UK’s negotiating position.
He told talkRADIO’s Julia Hartley-Brewer that talk of tensions within cabinet was “damaging” for the UK during the negotiating period.
The Brexiteer said: “The Prime Minister was crystal clear back in January in the Lancaster House speech.
“And frankly if there are cabinet members who don’t agree with her then rather than carping from the sidelines or taking advantage of the Prime Minister’s holiday, they should resign and go back to the backbenches.
“Because what they’re doing is they’re damaging the negotiating position and leverage of the Prime Minister and David Davis, our chief negotiator.”
Mr Tice advocated for trading on World Trade Organisation [WTO] terms and insisted it would be better than any “bad deal” the European Union could offer Britain.
“When you go into a negotiation you have to be prepared to walk away otherwise you know it’s a guarantee you’ll end up with a bad deal,” he said.
“Our suggestion is that it’s quite right to try for a deal but that we should accelerate the negotiating process.”
The campaigner also raised concerns over UK politicians’ summer break.
He said: ”I think the negotiating team should be working frankly 24/7, seven days a week to get this agreement either done and resolved and agreed as soon as possible, definitely by Christmas, or we should walk away.”
The comments come after the former head of the diplomatic service swiped Britain’s Brexit negotiations so far, blasting reported conflicts within Mrs May’s cabinet for hindering talks.
Sir Simon Fraser, chief mandarin at the Foreign Office until 2015, told BBC Radio 4’s Westminster Hour the UK had so far been “a bit absent” from negotiations.
He told BBC Radio 4’s Westminster Hour: “The negotiations have only just begun, I don’t think they have begun particularly promisingly, frankly, on the British side.”
August 7th, 2017: Express