The Prime Minister (pictured in Downing Street today) met with her Brexit 'war cabinet' today after sixty Eurosceptic Tory MPs backed a 30-page report savaging the plan

Proposals for a customs partnership with the EU have been rejected at a meeting of Theresa May's 'war Cabinet' today, it has been reported.

New Home Secretary Sajid Javid and Defence Secretary Gavin Williamson are said to have expressed 'significant' and 'grave concerns' about the plans.

The rebuke came after Brexit-backing MPs mounted a huge effort to kill off proposals for a customs deal amid fear it would leave Britain too attached to the EU.

BBC political editor Laura Kuenssberg wrote that she has been told Mrs May requested 'revised proposals' and 'further work' on both proposals discussed at the meeting, contradicting other sources who claim the customs deal was rejected.

She added: 'So already different versions out there of what happened at the meeting - but certainly the proposals as they currently exist are not viable with Number 10 agreeing they need more work.'

Mrs May's allies, meanwhile, warned Brexiteers to wake up to 'reality' today as she battles to save a key plank of her plans for future trade with the EU.

Amid a massive revolt by Tory Eurosceptics, Cabinet Office minister David Lidington said they had to recognise the 'challenges' of forging a 'deep and special relationship' with the bloc.

David Davis and Boris Johnson (pictured left and right in Downing Street today) are hoping to join forces with Michael Gove Liam Fox to kill off the customs partnership proposal

BBC political editor Laura Kuenssberg wrote that she has been told Mrs May requested 'revised proposals' and 'further work' on both proposals discussed at the meeting, contradicting other sources who claim the customs deal was rejected

Downing Street has reportedly been warned in correspondence that accepting the customs partnership deal would bring about the 'collapse' of the Government. Pictured: Environment Secretary Michael Gove, who is said to be willing to form a united front against the plan

Senior Cabinet members including Boris Johnson, David Davis, Liam Fox and Michael Gove urged the premier to abandon the idea at a meeting of her 'War Cabinet' this afternoon - although a final decision has been delayed.

Housing minister Dominic Raab appeared to pre-judge the outcome of the crucial clashes - saying Brexiteers were 'winning the argument' against a customs partnership.

The standoff deepened today after sixty Conservative backbenchers sent a 30-page report to Downing Street savaging the proposal.

The damning report - compiled by the powerful European Research Group headed by Jacob Rees-Mogg - claimed the idea would 'festoon the entire economy with burdensome controls, while crippling the ability of the UK' to negotiate trade deals.

Mr Rees-Mogg insisted this morning that he was not 'threatening' Mrs May. But he warned that the proposal would 'not deliver on the Conservative Party manifesto or the Prime Minister's other commitments'.

'It would leave us de facto in the customs union and the single market,' he told BBC Radio 4's Today programme.

Mr Lidington said the PM was 'listening' to her MPs. But in a stark message, he added: 'Part of the future deal we are looking for with the European Union will be a customs agreement/partnership of some kind, some new arrangement to replace the customs union which we are leaving.'

He told ITV's Good Morning Britain he was 'not interested in slogans' but wanted to protect jobs and living standards.

'The challenge that we have got is to have a deep and special partnership with the EU,' he added.

Supporters of the customs partnership concept believe it is the only way of protecting the economy and avoiding a hard Irish border.

But Downing Street has been warned that trying to force the plan through would bring about the 'collapse' of the Government.

If 60 MPs turned against Mrs May it would destroy her wafer thin Commons majority of 13 - and could bring her premiership to an end.

One European Research Group source told The Telegraph: 'We have swallowed everything so far – but this is it.

Liam Fox (pictured in Downing Street today) stopped short of saying explicitly that he would quit if Mrs May changed course, but left little doubt about his intentions

'If they don't have confidence in Brexit we don't have confidence in them. The Prime Minister will not have a majority if she does not kill off the NCP [New Customs Partnership].'

Brexiteers fear Mrs May will side with Mr Hammond, Business Secretary Greg Clark and her chief Brexit adviser Olly Robbins, who are championing the idea.

Mr Lidington played down the prospect of any final decision on the Brexit 'war cabinet'.

He told BBC Radio 4's Today the discussions would 'start this afternoon and will probably continue in other meetings'.

The two proposals had been the subject of 'intensive analytical work by civil servants' who had been 'looking at the practicalities, the operational challenges that would have to be surmounted, all these problems - the legal risks and so on'.

'This will be the first time today for Cabinet colleagues to sit down and have a constructive discussion about the way forward,' he said.

Mr Lidington added: 'I expect we will come to a decision on this, as well as on other important elements of our negotiating position, over the next few weeks.'

He indicated that the full Cabinet may be invited to consider the position by Mrs May after the Brexit sub-committee has discussed the options.

She was also 'talking all the time and listening all the time to voices of Conservative MPs, Conservative Party supporters, from all strands of the debate about Europe'. He added that before June's summit of EU leaders 'we need to be making every effort to ensure there is significant progress in the negotiations'.

The leading Brexiteers fear it would effectively keep the UK inside the EU's customs union and wreck hopes of an independent trade policy.

'The four are unambiguous in thinking this is a terrible idea,' the source said.

Mr Gove has described the plan as 'bonkers' and Dr Fox yesterday hinted he could even resign if it went ahead.

Mr Davis, who has dismissed the proposal as 'blue sky thinking', is also reported to have told friends he could quit. Aides played down the prospect of a walk-out however.

The four hope to 'peel off' Defence Secretary Gavin Williamson and new Home Secretary Sajid Javid, both former Remainers.

The two options now on the table New Customs Partnership —backed by Remainers It would involve UK officials electronically tracking final destinations of goods coming to Britain. Those heading for Europe would pay the relevant EU tariff and the money handed over to Brussels. Firms selling to the UK would be eligible for a refund, if our tariff levels were lower. In theory, the EU would have to make similar arrangements at its borders to track goods destined for the UK. If it works – and many believe it won't – it would theoretically allow the UK to leave the customs union and negotiate trade deals with non-EU countries. Crucially, by removing all physical EU-UK customs borders it would also provide the answer to the Ulster border. Maximum Facilitation — supported by Brexiteers This would attempt to dramatically reduce customs controls and barriers between the UK and the EU. Goods would be electronically tracked and pre-cleared with the tax authorities. Firms allowed to operate as 'trusted traders' – so they can move goods freely without having to pay duty every time goods moved across the border. Officials admit this will be more bureaucratic than inside customs union but hope to create a 'bespoke' model. It would allow Britain to do deals with non-EU nations, because we would not have to comply with EU tariffs. But the EU has dismissed this proposal as 'magical thinking'. Advertisement

Jacob Rees-Mogg urged the Prime Minister to abandon the partnership plan and challenge Remainers in Parliament who want to keep Britain inside the customs union.

The Eurosceptic MP said the partnership proposal, which has the backing of Chancellor Philip Hammond, would 'result in the worst of all worlds and make us a vassal state'.

One Whitehall source said the PM was more concerned about the prospect of a defeat in Parliament by diehard Remainers led by former attorney general Dominic Grieve than by the risk of a mutiny by Tory Eurosceptics.

'The bottom line is, she is more afraid of Grieve than she is of Iain Duncan Smith,' the source said.

Cabinet sources played down the prospect of immediate resignations, suggesting Eurosceptic ministers would rely on Brussels killing off the proposal later in the year.

Opinion in Mrs May's 11-strong Brexit war cabinet is finely balanced. Friends of Mr Javid acknowledge he has held 'bracingly Eurosceptic' views for years, but point out that he is a pragmatist who ended up backing Remain in 2016.

Mr Williamson is opposed to the UK remaining in any customs union. But allies suggested he could be swayed by his loyalty to the PM. Today's meeting has been called to discuss the Government's two options for future customs dealings with the EU.

The 'new customs partnership' would require officials to track the final destination of all goods entering the UK and hand over relevant tariffs to Brussels on goods ending up in the EU. It would also require alignment with EU regulations in some sectors.

The second option – known as 'maximum facilitation' – is a looser arrangement, which would use technology to streamline customs controls, particularly at the Irish border.

The four hope to 'peel off' Defence Secretary Gavin Williamson (pictured today) and new Home Secretary Sajid Javid, both former Remainers

The Prime Minister is expected to warn ministers the proposal is the only one that can resolve the Northern Ireland border problem and get through Parliament

The damning report - compiled by the European Research Group, which is led by Jacob Rees-Mogg (pictured) - claimed the plan would 'festoon the entire economy with burdensome controls, while crippling the ability of the UK' to negotiate trade deals

The EU has raised doubts about whether controls could ever be seamless enough to prevent the need for a hard border on the island of Ireland.

Eurosceptic MPs have warned that Mrs May could face a leadership challenge unless she opts for a clean break with Brussels. One former minister said: 'This would be the final straw.'

Unconfirmed reports earlier this month suggested that EU officials had dismissed both UK proposals. Mr Davis yesterday told the House of Lords EU committee: 'The Commission did push back on both.'

What is a customs partnership with the EU? A customs partnership is less formal than the current EU customs union the UK is a member of. Under the proposals, Britain would stay in a customs union with the EU for some sectors, while leaving it for others. This would mean it would impose the same tariffs as the Brussels bloc on some goods, but set its own on others. Backers of the plan say his would facilitate free trade in areas where Britain does a lot of its business with the EU, while freeing the country to sign new free trade deals with other countries. One possibility could be keeping the UK and EU in a customs union for trade in goods, but allowing divergence for the services sector. Under the so-called 'hybrid model', the UK would collect EU import tariffs on behalf of Brussels and then pay it to the EU. But Brexiteers are critical of the plan. which they think is unworkable and cumbersome. They fear it will effectively stop the UK from being able to negotiate free trade deals around the world after Brexit. Advertisement

Downing Street fears the Government's hands could be tied if Remainers in Parliament rally round an amendment to the Trade Bill tabled by former Tory Minister Anna Soubry to keep Britain in a customs union.

Insiders believe the partnership idea could buy off enough rebels to avoid defeat.

Downing Street last night insisted the scheme could be delivered on time.

A No 10 spokesman said: 'We are leaving the customs union and won't be joining a customs union. We have put forward two proposals for addressing the customs issue in general and they will be discussed by the Government further.'

Yesterday, Dr Fox ramped up the pressure on May over Brexit - making clear he is ready to quit if she drops her red line on leaving the customs union.

The Trade Secretary said any form of customs union with the EU would be 'unacceptable' and worse than the UK's current membership terms with the bloc.

The PM has repeatedly pledged that there will be no customs union after Brexit, but is struggling to find a way of reconciling the demands of Brexiteers and Remainers.

Tory rebels are threatening to side with Labour and other parties in a Commons vote on staying in the customs union expected next month.

They say keeping the ties are the only way to protect the economy and prevent a hard Irish border.

The Lords has already passed an amendment to the EU Withdrawal Bill designed to maintain a customs union - although ministers believe it is so loosely worded as to have little real impact.

But Eurosceptic Tories say they could move against Mrs May unless she holds the line on the crucial issue and ensures the UK can strike trade deals around the rest of the world.

The PM - pictured chatting with pupils at Brooklands Primary School in Sale, Manchester yesterday - is facing a battle to hold the Cabinet together behind her Brexit plans

Trade Secretary Liam Fox (pictured right arriving for Cabinet with Boris Johnson today) said any form of customs union with the EU would be 'unacceptable'

Mr Javid, pictured on his way to work this morning, is set to play a crucial role in the looming clashes over a future trade deal with the EU. But Ms Rudd, pictured leaving her London home today, has returned to the backbenches

Amber Rudd was thought to have been backing Mrs May ahead of a crunch showdown on the customs union in the Brexit 'war Cabinet' sub-committee (pictured together in February). But it is unclear where Mr Javid will fall on the issue

WHO'S IN BREXIT WAR CABINET AND WHERE DO THEY STAND? Prime Minister Theresa May Backed Remain, has since insisted she will push through Brexit, leaving the single market and customs union. Cabinet Office Minister David Lidington A strong Remainer during the referendum campaign, recently made clear he has not changed his mind about it being better if the country had chosen to stay in the bloc. Chancellor Philip Hammond Seen as one of the main advocates of 'soft' Brexit in the Cabinet. Has been accused of trying to keep the UK tied to key parts of the customs union for years after the transition ends. Home Secretary Sajid Javid Brought in to replace Amber Rudd after she resigned amid the Windrush scandal, Mr Javid was seen as a reluctant Remainer in the referendum. Many thought the former high-flying banker would plump for the Leave campaign, but he eventually claimed to have been won over by the economic case. He is likely to focus be guided by evidence about trade calculations in discussions over how closely aligned the UK should be with the EU. Foreign Secretary Boris Johnson The Brexit champion in the Cabinet, has been agitating for a more robust approach and previously played down the problems of leaving with no deal. He is unhappy with plans for a tight customs arrangement with Brussels - warning that it could effectively mean being lashed to the EU indefinitely. Environment Secretary Michael Gove Has buried the hatchet with Mr Johnson after brutally ending his Tory leadership campaign in the wake of David Cameron's resignation. Thought to be less concerned with short term concessions that Mr Johnson, but focused on ensuring the UK is free from Brussels rules in the longer term. Brexit Secretary David Davis A long-time Eurosceptic and veteran of the 1990s Maastricht battles, brought back by Mrs May in 2016 to oversee the day-to-day negotiations. He has said the government will be seeking a 'Canada plus plus plus' deal from the EU. International Trade Secretary Liam Fox Another Brexiteer, his red lines are about the UK's ability to strike trade deals with the rest of the world, and escaping Brussels red tape. Business Secretary Greg Clark On the softer Brexit side of the Cabinet, Mr Clark has supported Mr Hammond's efforts to maintain close links with the customs union. Defence Secretary Gavin Williamson A close ally of the Prime Minister and viewed by some as her anointed successor. He is believed to be siding with the Brexiteers on customs arrangements and the need for Britain to be able to diverge from EU rules. Northern Ireland Secretary Karen Bradley Supported Remain but a relatively unknown quantity on the shape of a deal. Replaced James Brokenshire, another May loyalist, after he resigned on health grounds last month. Advertisement