Rebel Tory MPs believe they now have sufficient support to force Theresa May into effectively keeping the UK in the single market.

Conservatives have told The Independent there would be enough of their party’s MPs to lock in full single market access after Brexit, as long as Labour also backs it.

But in a move set to enrage Labour politicians, Jeremy Corbyn’s front bench will on Tuesday refuse support for just such a proposal in the Lords – preventing it from being voted on in the Commons.

Mr Corbyn is now being warned he risks a major internal row and must explain to pro-EU party members why he is “throwing away a clear opportunity” to defeat Ms May’s plans to abandon the single market.

It follows reports that Tory chief whip Julian Smith has already told the prime minister she lacks numbers in the Commons to defeat rebel amendments aimed at keeping the UK in an EU customs union.

Tory rebels, who joined forces with Labour to shift the government towards closer customs relations with Europe, will now push Ms May towards remaining inside the European Economic Area (EEA) and the European Free Trade Association (EFTA) – which would deliver full single market access.

They say up to 15 Conservative backbenchers are now certain it is the best way to ensure the UK’s economic strength, while also staying true to the 2016 referendum result.

Theresa May: 'We're leaving the single market... in certain ways access will be different to what it is now'

One senior Conservative backbencher told The Independent: “Yes, we have the numbers now, but it will depend on exactly how any particular amendment is phrased.

“It’s more difficult than passing a customs union amendment, because the [Conservative] manifesto was clear about leaving the single market.

“But undoubtedly there are a group of Conservative MPs, now larger than the one who voted for similar amendments in the past, who have concluded maybe it is a way for us to go.”

A vote designed to commit the government to the EEA/EFTA path was lost in December in the Commons, but MPs say things have now changed.

Another Conservative rebel told The Independent: “We have more numbers for this than we had at the defeat in December.

“There are a gang of people who have started saying they are keen on it, a group, up to 15 of us, who think this may well be a good way out.”

Keir Starmer: Brexit deal means UK will be tied to single market 'in perpetuity'

Former chancellor Ken Clarke backed the single market in the December vote along with Anna Soubry MP, while other known rebels such as Nicky Morgan, Antoinette Sandbach, Jeremy Lefroy, Paul Masterton and Dominic Grieve have all spoken in debates in favour of the EEA/EFTA route since.

Others who have made supportive comments for the option include Caroline Spelman, Heidi Allen, James Cartlidge, Kevin Hollinrake and John Stevenson. Rebels also say two cabinet members are sympathetic to the idea.

The EEA/EFTA route would also allow the government to escape the European Court’s jurisdiction, but would mean the UK having, to a large extent, to accept the EU’s “four freedoms”.

But Tory rebels argue Britain would have more power than it currently does to impose restrictions on immigration – a driving motivation behind the Leave vote.

Barnier: 'the single market cannot be a la carte'

Former Conservative minister Stephen Hammond told The Independent: “It allows you to have some conversations over new regulation, in that you are consulted and are part of the process before it comes in, though it’s still not co-determination, of course.

“But the other reason I think it’s a good idea, is that if you look at the EEA terms of reference, it is clear there is more leeway to impose restrictions on freedom of movement.”

They want him to put forward the case for remaining in a strong relationship with Europe. He has got to stand up and represent them Labour peer Waheed Alli on Jeremy Corbyn

The next opportunity to push the government down the EEA/EFTA route comes on Tuesday, when there will be a vote on an amendment to the EU Withdrawal Bill tabled in the Lords by Labour peer Waheed Alli.

Remain-backing Labour MPs want the amendment passed in the Lords, so they can then team up with Tory rebel MPs in the Commons and prevent the government overturning it – in the same way they look set to with other Brexit amendments.

But a Labour front bench source in the Lords confirmed the Alli amendment would not have the party’s official support, saying: “It’s not going to go through. It’s not going to the Commons.”

Brexit so far: in pictures Show all 53 1 / 53 Brexit so far: in pictures Brexit so far: in pictures Brexit campaign Boris Johnson led the VoteLeave campaign PA Brexit so far: in pictures Brexit campaign Boris Johnson MP, Labour MP Gisela Stuart and UKIP MP Douglas Carswell address the people of Stafford in Market Square during the Vote Leave Brexit Battle Bus tour on 17 May 2016. Their lead line on the tour was: “We send the EU £350 million a week, let's fund our NHS instead.” Getty Brexit so far: in pictures Voting day A man shelters from the rain as he arrives at a polling station in London on 23 June 2016. Millions of Britons voted in the referendum on whether to stay in or leave the European Union AFP/Getty Brexit so far: in pictures Referendum results Leader of Ukip, Nigel Farage, reacts at the Leave EU referendum party at Millbank Tower in central London as results indicated that it was likely the UK would leave the European Union AFP/Getty Brexit so far: in pictures Protesting the result A young couple painted as EU flags and a man with a sign reading “I’m not leaving” protest outside Downing Street against the voters decision to leave the EU on 24 June 2016 Getty Brexit so far: in pictures David Cameron resigns British Prime Minister David Cameron resigns on the steps of 10 Downing Street on 24 June 2016 after the results of the EU referendum were declared and the United Kingdom voted to leave the European Union Getty Brexit so far: in pictures Theresa May Becomes the new Conservative Party leader Theresa May receives a kiss from her husband Philip, after becoming the new Conservative Party leader on 11 July 2016. May became Prime Minister two days later and although she voted to remain in the referendum was keen to lead Britain’s Brexit talks after her only rival in the race to succeed David Cameron pulled out unexpectedly. May was left as the only contender standing after the withdrawal from the leadership race of Andrea Leadsom, who faced criticism for suggesting she was more qualified to be prime minister because she had children AFP/Getty Brexit so far: in pictures Lancaster House keynote speech on Brexit British Prime Minister Theresa May delivers her keynote speech on Brexit at Lancaster House in London on 17 January 2017. Where she spoke about her offer to introduce a transition period after the UK formally leaves the European Union in March 2019. Despite repeating the pro-Brexit mantra of “no deal is better than a bad deal”, the Prime Minister claimed she wanted a “tone of trust” between the negotiators and said Britain was leaving the EU but not Europe. She said there should be a clear double lock needed for the transitional period to make sure businesses had time to prepare for changes to their trading relationships with the EU Getty Brexit so far: in pictures Triggering of Article 50 British Prime Minister Theresa May in the cabinet, sitting below a painting of Britain's first Prime Minister Robert Walpole, signs the official letter to European Council President Donald Tusk invoking Article 50 and the United Kingdom's intention to leave the EU on 29 March 2017 Getty Brexit so far: in pictures Gibraltar nonsense Tensions have risen over Brexit negotiations for the Rock of Gibraltar. The European Council has said Gibraltar would be included in a trade deal between London and Brussels only with the agreement of Spain. While former Conservative leader Michael Howard claimed that Theresa May would be prepared to go to war to protect the territory. Spain's foreign minister stepped in only to assert that there was no need for the dispute Getty Brexit so far: in pictures Shock snap election Soon after triggering Article 50, Theresa May called on 18 April 2017 for a snap general election. The election would be on 8 June and it came as a shock move to many, with her reasoning to try to bolster her position before tough talks on leaving the EU AFP/Getty Brexit so far: in pictures Dissolution of Parliament for General Election Campaign Prime Minister Theresa May makes a statement in Downing Street after returning from Buckingham Palace on 3 May 2017. The Prime Minister visited the Queen to ask for the dissolution of Parliament signalling the official start to the general election campaign Getty Brexit so far: in pictures Conservatives lose parliamentary majority An arrangement of British daily newspapers showing front page stories about the exit poll results of the snap general election. British Prime Minister Theresa May faced pressure to resign on 9 June 2017 after losing her parliamentary majority, plunging the country into uncertainty as Brexit talks loomed. The pound fell sharply amid fears the Conservative leader would be unable to form a government AFP/Getty Brexit so far: in pictures Labour gains Britain’s opposition Labour Party leader Jeremy Corbyn gives a tumbs up as he arrives at Labour headquarters in central London on 9 June 2017 after the snap general election results showed a hung parliament with Labour gains and the Conservatives losing their majority AFP/Getty Brexit so far: in pictures Brexit negotiations begin Brexit Minister David Davis and European Commission member in charge of Brexit negotiations Michel Barnier address a press conference at the end of the first day of Brexit negotiations in Brussels on 19 June 2017 AFP/Getty Brexit so far: in pictures May speaks in Florence British Prime Minister Theresa May speaks on 22 September 2017, in Florence. May sought to unlock Brexit talks after Brussels demanded more clarity on the crunch issues of budget payments and EU citizens' rights AFP/Getty Brexit so far: in pictures EU council summit – insufficient progress German Chancellor Angela Merkel joins other EU leaders for a breakfast meeting during an EU summit in Brussels on 20 October 2017. The EU spoke about Brexit and announced that insufficient progress had been made AFP/Getty Brexit so far: in pictures DUP derails settlement on the withdrawal part of Brexit DUP Deputy Leader Nigel Dodds walks off after speaking to members of the media as a protester holding flags shouts after him outside the Houses of Parliament on 5 December 2017. British Prime Minister Theresa May was forced to pull out of a deal with Brussels after the DUP said it would not accept terms which see Northern Ireland treated differently from the rest of the UK Getty Brexit so far: in pictures May suffers defeat over EU (Withdrawal) Bill Theresa May suffers defeat in parliament over EU (Withdrawal) Bill on 13 December 2017. The Government was defeated by Conservative rebels and Labour MPs in a vote on its key piece of Brexit legislation. MPs amended the EU (Withdrawal) Bill against Theresa May's will, guaranteeing Parliament a “meaningful” vote on any Brexit deal she agrees with Brussels. Ms May's whips applied pressure on Conservative rebels who remained defiant in the Commons throughout the day and in the end the Government was defeated by 309 votes to 305 Brexit so far: in pictures EU council summit – sufficient progress Britain's Prime minister Theresa May arrives to attend the first day of a European union summit in Brussels on 14 December 2017. European leaders discussed Brexit and announced there was finally sufficient progress at the end of the two days AFP/Getty Brexit so far: in pictures The game moves to transition Brexit Secretary David Davis gives evidence on developments in European Union divorce talks to the Commons Exiting the EU Committee in Portcullis House, London, on 24 January 2018 PA Brexit so far: in pictures Trade deal is what May wants French President Emmanuel Macron gestures to Britain's Prime Minister Theresa May after they hold a press conference at the Royal Military Academy, Sandhurst, on 18 January 2018. May and Macron agreed a new border security deal, through which the UK will pay more to France to stop migrants trying to reach British shores on 18 January 2018 AFP/Getty Brexit so far: in pictures Transition period agreed The UK and EU agree terms for Brexit transition period on 19 March, 2018 Reuters Brexit so far: in pictures No agreement on Irish border The EU and UK however failed to reach an agreement on the Irish border during the successful talks on other Brexit issues AFP/Getty Brexit so far: in pictures EU attacks May’s ‘fantasy’ strategy For months after the March deal is struck there is little significant progress in talks. One senior EU official tears into Britain’s ‘fantasy’ negotiating strategy and accuses Theresa May of not even having a position on a variety of important issue Getty Brexit so far: in pictures UK releases Ireland plan Britain releases a new customs plan to solve the Northern Ireland border but Michel Barnier says it leaves ‘unanswered’ questions and would not prevent a hard border EbS Brexit so far: in pictures Chequers plan agreed The cabinet agrees on a plan known as the "Chequers deal" on July 6 2018. The plan seeks regulatory alignment on goods and food, divergence on services, freedom from the European Courts of Justice and an end to free movement. Many were surprised that the hard Brexiteers of the cabinet would agree to this plan PA Brexit so far: in pictures Chequers plan sparks resignations Brexit Secretary David Davis and Foreign Secretary Boris Johnson and numerous ministers resign in the days following the Chequers agreement Reuters Brexit so far: in pictures Davis out, Raab in On 9 July, Dominic Raab replaces David Davis as Brexit Secretary. Raab is a keen Brexiteer and was a housing minister before taking over from Davis Reuters Brexit so far: in pictures Barnier's "deal like no other" EU chief negotiator Michel Barnier claims on August 29 2018 that they are prepared to offer Britain a trade deal like no other, though he stressed that they will not divide or change the single market to accommodate Britain AP Brexit so far: in pictures "My deal or no deal" In an interview on Panorama on September 17, the Prime Minister insists that any Brexit deal will be offered to the EU on her terms. She asserts this amongst continued attacks on her approach to Brexit by Boris Johnson and the European Research Group, headed by Jacob Rees Mogg BBC/Jeff Overs Brexit so far: in pictures EU leaders reject Chequers Quite the blow was dealt to the Prime Minister at a EU leaders summit in Salzburg on September 20. European Council President Donald Tusk stated that the Chequers deal "will not work" Reuters Brexit so far: in pictures May demands respect Following the rejection of her Chequers plan the day before, the Prime Minister voiced her anger that the EU had dismissed it without offering an alternative. She stated that “throughout this process, I have treated the EU with nothing but respect. The UK expects the same. A good relationship at the end of this process depends on it." Getty Brexit so far: in pictures People's Vote march As the People's Vote campaign and The Independent's Final Say campaign gain traction, 700,000 people turn out in London to demand a final say on the UK's Brexit deal on October 20 2018 PA Brexit so far: in pictures More resignations As the Prime Minister settles on a Brexit deal, Brexit secretary Dominic Raab resigns along with Work and Pensions secretary Esther McVey and many other ministers Getty Brexit so far: in pictures Final Say petitions delivered to Downing Street People's Vote supporting MPs Chukka Umunna, Justine Greening and Caroline Lucas and The Independent editor Christian Broughton deliver over a million signatures in favour of a People's Vote to the Prime Minister at 10 Downing Street on December 3 2018 PA Brexit so far: in pictures May delays vote On December 10, the Prime Minister delayed the vote on her Brexit deal as it was near certain not to pass through the Commons due to Tory rebels and lack of DUP support AFP/Getty Brexit so far: in pictures No confidence motion Tory MPs triggered a confidence vote in the Prime Minister on December 12. She won by 200 votes to 117 Reuters Brexit so far: in pictures Commons rejects the deal Following the delay, the Prime Minister's deal was rejected in the Commons by a historic 230 votes AFP Brexit so far: in pictures Corbyn tables a no confidence motion Following the rejection of the Prime Minister's deal, opposition leader Jeremy Corbyn tabled a motion of no confidence in the government, which the government won by a margin of 19 AFP/Getty Brexit so far: in pictures Plan B The Prime Minister won the support of the commons to return to Brussels to renegotiate the backstop on January 29. In the same sitting, MPs also voted against a no-deal Brexit in a non-legally binding motion PA Brexit so far: in pictures EU council president savages Brexit campaigners who failed to plan for departure: ‘Special place in hell’ There is a “special place in hell” for pro-Brexit campaigners who demanded Britain leave the EU without explaining how it should happen, Donald Tusk has said. The European Council president launched the scathing attack as he accused anti-EU campaigners of pushing for Brexit “without even a sketch of a plan how to carry it out safely.” Mr Tusk also dismissed suggestions that the EU could reopen negotiations over the controversial Northern Ireland backstop, dealing a blow to Theresa May‘s hopes of securing fresh concessions as she tries to get her exit deal through parliament. Speaking in Brussels alongside Irish taoiseach Leo Varadkar, Mr Tusk said: “I’ve been wondering what a special place in hell looks like for people who promoted Brexit without even a sketch of a plan how to carry it out safely.” He also tweeted the accusation moments later Getty Brexit so far: in pictures EU and UK announce talks to restart after Theresa May visits Brussels Both have agreed to restart Brexit talks to find “a way through” the deadlock in Westminster, following a visit by Theresa May to Brussels. In a joint statement the British government and European Commission said Ms May had had a “robust but constructive” meeting with president Jean-Claude Juncker, and that the pair would meet again before the end of the month. But the EU again refused to reopen the withdrawal agreement and its controversial backstop – with any negotiations expected to focus on the future relationship between the UK and EU instead Getty Brexit so far: in pictures Brexit strategy lost MPs voted down May's Brext plans, with a majority of 45. The prime minister did not appear in parliament to see another defeat PA Brexit so far: in pictures Labour and Conservative MPs resign and create the Independent Group Back row of Chris Leslie, Gavin Shuker, Chuka Umunna and Mike Gapes, middle row of Angela Smith, Luciana Berger and Ann Coffey and front row of Sarah Wollaston, Heidi Allen, Anna Soubry and Joan Ryan PA Brexit so far: in pictures Non-biding votes on amendments to Brexit motion On February 27 he house held a series of votes, unanimously calling for the UK and EU to guarantee citizens rights in a no-deal scenario AFP/Getty Brexit so far: in pictures Attorney General publishes legal advice A hammer blow for May as Geoffrey Cox said her renegotiated deal can still leave UK in backstop against its will. Mr Cox did say the prime minister’s efforts had reduced the risk of the UK being trapped in the backstop indefinitely. MPs went on to vote against her deal by 391 to 242 UK Parliament/PA Brexit so far: in pictures No-deal off the table MPs rejected a no-deal Brexit by 43 votes on March 13, with cabinet ministers rebelling in another humiliating defeat for Theresa May. A day later they voted in favour of the prime minister seeking an extension to Article 50 AFP/Getty Brexit so far: in pictures House speaker bans May from third Commons vote on same Brexit deal John Bercow sensationally told Theresa May he would stop her making another attempt to pass her Brexit deal unless she has secured changes. The Speaker said a further ‘meaningful vote’ would be ruled out of order if the motion was “the same or substantially the same’ – under an ancient convention to stop the government bullying parliament on issues MPs have rejected Parliament Live Brexit so far: in pictures May writes to Tusk The prime minister wrote to Donald Tusk, president of the European Council, to ask for a three-month extension to give her more time to try to get her deal through parliament. However the European Commission advises the EU27 should offer a short extension to May 23 or a longer one meaning the UK would participate in European elections 10 Downing Street/AFP/Getty Brexit so far: in pictures European Council summit Theresa May’s request to extend triggering Article 50 until the end of June was rejected by the EU, and instead offered a shorter time frame. She accepted the offer of a delay until May 22 if her withdrawal deal is approved by Parliament. If MPs rejected it for a third time, the EU said Britain must propose a new plan by April 12. Ms May said she will not support a long delay because it would mean Britain participating in elections for the European Parliament Getty Brexit so far: in pictures Brussels confirms preparations for a no-deal Brexit are completed They warned that it is “increasingly likely” the UK will crash out. In a statement the European Commission (EC) said “preparedness and contingency work”, which the EC has been conducting since December 2017, was now finished. The announcement came days after EU leaders agreed to a request by Theresa May to extend the UK’s Brexit date AFP Brexit so far: in pictures May resigns British Prime Minister Theresa May reacts as she delivers a statement in London, Britain, May 24, 2019. REUTERS/Simon Dawson SIMON DAWSON Reuters

A Commons frontbench Labour source added: “We don’t believe the EEA/EFTA model is the right one to pursue.

“It was right 25 years ago, it’s right for Norway, but the UK is a different country, a different economy and we’ve never been satisfied that’s the right approach.”

But entrepreneur Lord Alli said that the Labour front bench’s approach “doesn’t make sense”, arguing it is essential for a UK economy heavily reliant on services to be in the EEA, as well as a customs union for goods.

He pointed out that his proposals are backed by founder of Cobra Beer Lord Bilimoria, a crossbench peer, and Tory peers Baroness Verma and Baroness McGregor-Smith, ex-CEO of Mitie Group, adding: “We come from a business background.”

House of Lords defeat Government on EU customs union withdrawal bill

The peer went on: “The front bench of both the Labour and Tory parties are united by the fact that they can’t make clear decisions on the EU, because they don’t want to upset the political balance of their rank and file.

“But Jeremy Corbyn needs to take a decision about our position on Europe. The people that support Labour are pro-European and, make no mistake, when you throw light on his position people are going to see that he still needs to come to the right place.

“They want him to put forward the case for remaining in a strong relationship with Europe. He has got to stand up and represent them.”

One Labour MP who also wants the party’s leadership to back Alli’s proposals, said: “If they don’t there will be a big row. Labour peers will be under heavy pressure to rebel.

“The leadership needs to be honest with members that it is throwing away a clear opportunity to defeat the government’s Brexit plans and ensure full benefits of the single market.”

The biggest issues facing UK on leaving EU Show all 8 1 / 8 The biggest issues facing UK on leaving EU The biggest issues facing UK on leaving EU Post-Brexit immigration workers sorting radishes on a production line at a farm in Norfolk. One possible post-Brexit immigration scheme could struggle to channel workers towards less attractive roles - while another may heighten the risk of labour exploitation, a new report warns. PA The biggest issues facing UK on leaving EU Customs union A key point in the negotiations remains Britain's access to, or withdrawal from, the EU customs union. Since the referendum there has been hot debate over the meaning of Brexit: would it entail a full withdrawal from the existing agreement, known as hard Brexit, or the soft version in which we would remain part of a common customs area for most goods, as Turkey does? No 10 has so far insisted that “Brexit means Brexit” and that Britain will be leaving the customs union, but may be inclined to change its position once the potential risks to the UK’s economic outlook become clearer. Alamy The biggest issues facing UK on leaving EU Northern Ireland-Irish border Though progress was made last year, there has still been no solid agreement on whether there should be a hard border between Northern Ireland and the Republic of Ireland. To ensure borderless travel on the island, the countries must be in regulatory alignment and therefore adhere to the same rules as the customs union. In December, the Conservative Party’s coalition partners, the DUP, refused a draft agreement that would place the UK/EU border in the Irish Sea due to its potential to undermine the union. May has promised that would not be the case and has suggested that a “specific solution” would need to be found. Getty The biggest issues facing UK on leaving EU Transition period Despite protests from a small number of Conservative MPs, the Government and the EU are largely in agreement that a transitional period is needed after Brexit. The talks, however, have reached an impasse. Though May has agreed that the UK will continue to contribute to the EU budget until 2021, the PM wants to be able to select which laws made during this time the UK will have to adhere to. Chief negotiator Michel Barnier has said the UK must adopt all of the laws passed during the transition, without any input from British ministers or MEPs. EPA The biggest issues facing UK on leaving EU Rights of EU citizens living the UK The Prime Minister has promised EU citizens already living in the UK the right to live and work here after Brexit, but the rights of those who arrive after Brexit day remains unclear. May insists that those who arrive during the transition period should not be allowed to stay, whereas the EU believe the cut-off point should be later. Getty The biggest issues facing UK on leaving EU Future trade agreement (with the EU) Despite this being a key issue in negotiations, the Government has yet to lay out exactly what it wants from a trade deal with the EU. Infighting within the Cabinet has prevented a solid position from being reached, with some MPs content that "no deal is better than a bad deal" while others rally behind single market access. The EU has already confirmed that access to the single market would be impossible without the UK remaining in the customs union. Getty The biggest issues facing UK on leaving EU Future trade agreements (internationally) The Government has already begun trying to woo foreign leaders into prospective trade agreements, with various high profile state visits to China, India and Canada for May, and the now infamous invitation to US President Donald Trump to visit London. However the UK cannot make trade agreements with another country while it is still a member of the EU, and the potential loss of trade with the world's major powers is a source of anxiety for the PM. The EU has said the UK cannot secure trade deals during the transition period. EPA The biggest issues facing UK on leaving EU Financial services Banks in the UK will be hit hard regardless of the Brexit outcome. The EU has refused to give British banks passporting rights to trade within the EU, dashing hopes of a special City deal. However according to new reports Germany has suggested allowing trade on the condition that the UK continues paying into the EU budget even after the transition period. Getty

If Lord Alli’s amendments are defeated on Tuesday and never make it to the Commons, then Tory rebels say they are preparing their own amendments to table to other pieces of legislation at a later stage.

A government spokesperson said: “The referendum was a vote to take control of our borders, laws and money. Ongoing participation in the EEA would mean having to implement new EU legislation automatically and in its entirety without having a say on how it is formulated – and it would also mean continued free movement.