Tensions within the Tory party over Brexit have boiled over, with a former minister accusing influential backbencher Jacob Rees-Mogg and his allies of plotting a “coup” to oust Theresa May.

Former justice minister Phillip Lee, who resigned from the Government over Brexit, said there was “no doubt” that Eurosceptics were mobilising and called on colleagues to “stand against this nonsense”.

Meanwhile European leaders stepped up pressure on Mrs May to provide answers on her Brexit plans as she prepared for Friday’s Chequers showdown with her Cabinet.

Chequers
The crunch Cabinet meeting will take place at Chequers (Suzanne Plunkett/PA)

The Prime Minister was told by Dutch counterpart Mark Rutte to provide clarity on “every aspect” of the UK’s future relationship with the EU, while European Council president Donald Tusk called for “realism” if a Brexit deal is to be reached this year.

Ill-feeling within the Tory party has focused on the role played by Mr Rees-Mogg, leader of the pro-Brexit European Research Group of MPs.

On Monday, Foreign Secretary Boris Johnson gave him support after a backlash from senior Tories for saying the Prime Minister must deliver the Brexit she promised or risk collapsing her Government.

In a fresh warning on Tuesday, Mr Rees-Mogg said MPs would not vote for a Brexit deal which failed to meet Mrs May’s stated red lines of leaving the single market, customs union and jurisdiction of the European courts.

In a podcast for the ConservativeHome website, he said there had been a “breakdown in collective responsibility” in the Cabinet, with pro-EU ministers openly promoting solutions “against the Prime Minister’s speeches, against the position formally of the Cabinet and against the manifesto”.

He said: “I am trying to support the Prime Minister’s position and to remind people that any implementation deal has to get through Parliament, and if it is a bad deal, or it doesn’t meet the manifesto commitments, people won’t vote for it.”

He insisted he was not “personally ambitious” and was not aware of a £750,000 war chest reportedly raised by supporters for an eventual leadership bid.

But Dr Lee said: “We need courageous, rational leadership to get our country successfully through Brexit,” with “decisions based on reality and evidence, not dreams and dogma”.

“The last thing we need is a leadership challenge,” he said on Twitter.

“But when an MP & his supporters have collected £750k to do just that, there is no doubt that Brexiteers are planning a coup.

“I call on other rational members of the party to stand against this nonsense.”

The Chequers summit is aimed at fixing the Government’s position on key areas of the trade deal it wants with Brussels, but details remain vague on a reported “third way” to manage customs arrangements at ports and the Irish border.

Cabinet ministers have not been briefed on any alternative to the “new customs partnership”, which would see the UK collect tariffs on behalf of the EU, or the Brexiteers’ favoured “max fac” model involving streamlined arrangements and the use of technology to reduce friction.

Chancellor Philip Hammond, viewed as one of the Cabinet ministers favouring a soft Brexit, told the Commons: “We have to listen to what business is telling us and make sure that we deliver a Brexit which delivers the needs of business.”

The comments will be seen as a rebuke to the Foreign Secretary, who reportedly said “f*** business” when asked about Brexit fears.

Mr Hammond said ministers at Friday’s meeting will also be given Whitehall’s assessment of the economic implications of different Brexit options.

The countdown to Brexit
The countdown to Brexit

Cabinet tensions are high ahead of the Chequers gathering, with the potential for Brexiteer ministers such as Mr Johnson to quit unless they get their way.

Although decisions may be reached on issues relating to customs, other areas – such as how to respect the PM’s red line on ending European Court of Justice jurisdiction and free movement – may only be addressed through less concrete proposals.

A Cabinet source said: “In the speculation ‘will there be fudge, won’t there be fudge’ – I suspect there will be.”

Any lack of clarity would add to the frustration of EU leaders who increased pressure on Mrs May on Tuesday.

Mr Rutte, who had a meeting with the Prime Minister in The Hague, said: “We urgently need clarity about every aspect of the future relationship between the EU and the UK.”

In Strasbourg, Mr Tusk told MEPs: “The sooner we get a precise UK proposal on the Irish border, the better the chance to finalise the Brexit negotiations this year.”

He hoped the white paper would bring “the necessary clarity, realism and impetus to these negotiations”.

European Commission president Jean-Claude Juncker said “we have been waiting for months now for the white paper”.