Tory Eurosceptics have hit back at Theresa May by tabling amendments to a key Brexit Bill which could kill off her Chequers plan for future relations with the EU.
The four amendments to the crucial Customs Bill were put down a day before Thursday's publication of a White Paper setting out the British prime minister's plans, which infuriated Leavers and prompted the resignation of Cabinet ministers Boris Johnson and David Davis.
A rebellion by Eurosceptic backbenchers could wipe out Mrs May's majority when the Bill returns to the Commons on Monday, in what would be the first significant test of strength for her Brexit critics.
The PM insisted that the deal she agreed with her Cabinet at Chequers last week "delivers on the vote that people gave on Brexit" in the 2016 referendum.
But prominent Brexiteer Jacob Rees-Mogg described it as a "breakdown in trust" and said Mrs May must now U-turn or be forced to rely on Labour votes to get her legislation through Parliament.
One of the rebel amendments demands that the UK should scrap an offer - contained in the Chequers plan - to collect taxes and duties on behalf of the EU, unless the remaining 27 member states pledge to do the same for Britain.
A second - reportedly backed by the DUP - would force the British government to commit itself in law not to allow a customs border down the Irish Sea.
And others would require the UK to have a separate VAT regime from the EU and force the prime minister to table primary legislation if she wishes to keep Britain in the customs union.
Mr Rees-Mogg, who chairs the European Research Group of Eurosceptic Tories, told The Sun: "Unfortunately Chequers was a breakdown in trust. Brexit meant Brexit, but now it appears Brexit means remaining subject to European laws.
"I believe this will help the government stick to the promises it made.
"It may resolve the dilemma the prime minister faces. Does she rely on Labour votes to achieve Brexit or does she change her mind and go back to Lancaster House? Will she stick to her earlier words?"
The move came amid warnings that the PM was facing "guerrilla warfare" in Parliament from angry Tory backbenchers determined to block her plans.
Speaking at the Nato summit in Brussels, Mrs May insisted that her Chequers deal delivered on the "red lines" which she set out in her Lancaster House speech last year.
"It delivers on the vote that people gave on Brexit, it delivers the fact that we will have an end to free movement, we will have an end to the jurisdiction of the European Court of Justice in the UK, we won't be sending vast contributions to the EU every year, we'll be out of the Common Agricultural Policy, out of the Common Fisheries Policy," she said.
"We deliver that Brexit and we do it in a way that protects jobs and livelihoods and meets our commitment to Northern Ireland."
Amid growing discontent on the Tory backbenches, Brexiteer Andrea Jenkyns warned that more resignations could follow those of Mr Johnson, Mr Davis, Brexit minister Steve Baker, two Conservative vice-chairs and two parliamentary aides.
"I think if the prime minister makes further concessions with the EU then there will no doubt be more resignations from Brexiteers in the Cabinet, from junior ministers to PPSs, because there is only so much that you can give in a negotiation," she told BBC2's Newsnight.
Andrew Bridgen became the first Conservative MP to declare publicly that he has sent a letter of no confidence in Mrs May to the chairman of the backbench 1922 Committee, Sir Graham Brady. Some 48 letters are required to trigger a vote.
But leading Eurosceptic Bernard Jenkin played down the prospects of more walkouts from Mrs May's administration.
"For the record ... ERG is not expecting any further resignations, nor were we expecting any in the first place," said Mr Jenkin.
"Nor do we expect a leadership challenge. We are supporting Theresa for PM."
And former Conservative leader William Hague warned party rebels that voting against the Prime Minister's final deal could result in Brexit being indefinitely delayed or halted altogether.
Lord Hague told BBC Radio 4's Today programme: "When it comes to a vote sometime around the end of this year, let us say that Theresa May has done a deal that bears some resemblance to what was put forward at Chequers with the EU.
"If anyone in the Conservative Party is then thinking about voting that down, that is the point at which they are going to endanger everything they have been trying to achieve.
"There is a whole range of scenarios in which they get no Brexit, or an indefinitely delayed Brexit, or a change of government or a second referendum."
One disgruntled Tory MP even declined an invitation to watch England's World Cup semi-final clash with Croatia at 10 Downing Street because of his unhappiness with Mrs May's Brexit plans.
Crawley MP Henry Smith posted his invitation from Chief Whip Julian Smith on Twitter, adding: "Received this invite to watch tomorrow's England-Croatia World Cup semi-final in 10 Downing Street.
"Seeing as the prime minister isn't bringing Brexit home I'm concerned attending would be a bad omen for football coming home ... I'll pass."
