Theresa May appears to be facing a new Tory bid to topple her just as Brexit key clashes reach their climax - and the EU prepares an 'ambush' with new demands.

The Prime Minister faces a Commons showdown this Tuesday and Wednesday as MPs hold a string of crunch votes on her EU Withdrawal Bill .

Leave-backing MPs are likely to vote on her side - to stop Britain staying in the EU-aligned EEA or customs union.

But Brexiteers are also in despair at Mrs May's slow progress with Brussels, which dumped on her latest customs plan 24 hours after she sent it this week.

And Mrs May's deputy, David Lidington, risked worsening their fury today by admitting Britain could still be tied to EU rules in 2022.

One Tory told the Sun on Sunday "all bets are off" after the EU Withdrawal Bill has safely finished its journey through the Commons.

And former party chairman Grant Shapps , who led a coup against Mrs May last year, today said there is only a "30% to 40%" chance she will lead the Tories into the next general election in 2022.

(Image: REUTERS)

(Image: AFP)

(Image: Reuters)

It comes just as reports emerge that Theresa May could be forced into the greatest concession of all - immigration.

According to the Sunday Times, a European ambassador has warned the EU will put free movement back on the table ahead of the Tory conference in October.

This risks catching the PM at a moment of political weakness, coming just before she needs support ahead of MPs voting on her final Brexit plan.

Reports today claim the EU could try and force Britain to accept continued freedom of movement - something Mrs May has repeatedly said is a red line.

Days ago Brexit Secretary David Davis threatened to quit amid a Cabinet row about how to extend customs arrangements beyond 2020.

What is the Norway model? (Image: AFP) The Norway model refers to countries being members of the European Economic Area (EEA), but not the European Union. Remaining in the EEA would grant Britain all the freedoms of the EU’s internal market - including the free movement of goods and people. Norway is an EEA member, which is why it's called the Norway model. It means the country is bound by all the EU regulations for those areas, as well as policies on employment, the environment and consumer protection. But, like Norway, it means the country does not have a say in how those policies are formulated.

(Image: Getty Images Europe)

Mrs May managed to quell the revolt, by vowing to end her customs 'backstop' in December 2021, after a testy hour-long meeting with Mr Davis.

But since then the EU has hit back, saying such a deal is not possible.

Now a Tory source has told the Sunday Times: "Last week was a dress rehearsal."

Another said: "She thinks she's won. She's f***** anyway. She's toast."

The newspaper reported that Boris Johnson had been prepared to follow David Davis out the door this week if he had quit.

A source said: "There would have been at least one other cabinet level resignation, including a very big beast of exotic plumage".

Another source said: "It would have been bloody and brutal. He (DD) would have taken her over the cliff with him."

Mr Shapps, speaking to Sky News' Sophie Ridge, said it seemed "unlikely" Mrs May will still be PM by the end of 2022.

(Image: PA)

(Image: REUTERS)

He played down any prospect of an immediate challenge but demanded a quicker pace with “more decisions made, less waiting around for things”.

In a sign of turmoil brewing in the party, two Theresa May-supporting MPs publicly spoke out today in a bid to stop colleagues moving against her.

Remainer Amber Rudd and Brexiteer Iain Duncan Smith, both former ministers, warned any defeat of Mrs May could lead to the fall of the government and the rise of Jeremy Corbyn .

In a joint article, they warn failing to back Mrs May would "risk losing the precious chance to go on implementing policies that transform lives”.

Veteran Tory ex-Chancellor Ken Clarke said MPs were holding Theresa May to ransom.

He told the BBC "they are undermining her" and "would seek to replace her" if they weren't held up by two factors - that most Tories would still back Mrs May in a no confidence vote, and they can't decide on a successor.

Housing Minister Dominic Raab demanded ministers unite behind the PM - branding Boris Johnson "silly" for claiming Donald Trump could do a better job of Brexit.

(Image: REUTERS)

The 15 crunch Brexit votes that will make or break Theresa May (Image: Getty) MPs are holding a marathon two-day voting session on June 12-13 on the EU (Withdrawal) Bill - the law that enacts Brexit. Theresa May wants MPs to overturn 15 amendments, passed by the House of Lords, that would push Britain towards a much softer Brexit. It could make or break her premiership so she's been pleading for Tory Remain-backers not to vote against the government. But it's going to be massively confusing. To help you follow the drama, here's a summary of the original 15 Lords amendments to the EU (Withdrawal) Bill - and what they would achieve if they pass. Meaningful vote*: Would give MPs a 'meaningful vote' in Autumn 2018 on Theresa May's Brexit deal. This would give Parliament a specific power to decide what happens next if her deal is rejected. MPs could force her back to the negotiating table, for example, instead of crashing out with no deal. Backers insist they wouldn't use it to 'stop Brexit' - but that's exactly what Leavers fear will happen. (49, 19) Customs Union: Would force Tory ministers to take steps towards staying in an EU Customs Union - by making a statement on how they'd do it. This could stop Britain from striking trade deals around the world - but would prevent a hard border in Northern Ireland and keep free trade with the EU. (1, 1) Single market: Would force the Tory government to keep Britain in the European Economic Area (EEA) - which practically means keeping membership of the single market, and following nearly all its rules. This would likely continue free movement between Britain and the EU - almost as we see it today. (110A, 51) Brexit Day: Would remove the legal date of Brexit - 29 March 2019 - to let ministers change the date at the last minute if they don't have a deal. Leavers also fear this could be a tool to delay Brexit indefinitely. (95, 37) Northern Ireland*: Would give added protection to the Northern Ireland border - forcing ministers to obey the Good Friday Agreement, and keep the province in an EU customs union if it stops a hard border. (88, 25) Henry VIII powers 1: Would block Tory ministers from changing EU laws on several issues - employment, equality, health and safety, environmental or consumer rights - without enhanced scrutiny by MPs. (11, 4) Henry VIII powers 2: Would block ministers having a wide-ranging power to decide when EU laws can be challenged after Brexit. (18, 52) Henry VIII powers 3: Limits ministers' power to change law without a vote - they'd only be able to do it "if necessary", instead of "if appropriate". (31, 10) Henry VIII powers 4: Would give a 'sifting committee' of MPs the power to insist Parliament gets a vote on legal changes. (70, 110) Refugees' rights*: Would continue refugees' rights to be reunited with their families in the UK under the EU's Dublin Regulation. (59, 24) Citizens' EU legal rights*: People could continue suing the government in UK courts for breaching "general principles" of EU law. (19, 53) Charter of Fundamental Rights: Would ensure the vast majority of the EU's Charter stays in UK law. (15, 5) Theresa May's mandate: Would force the PM to get MPs' approval for her 'mandate' for Britain's future relationship with the EU. (51, 20) Future EU laws: Would let ministers "copy and paste" new EU laws into UK law after Brexit, and carry on taking part in EU agencies. (93, 32) Protecting the environment: Would block ministers from using Brexit to water down any protections for the environment. (1, 3) For geeks, each amendment's 'number' is in brackets. As if it wasn't confusing enough, each one gets 'renumbered' so we've included both numbers - the old number, followed by the new number. Some of the above will be overturned, some could pass if there's a Tory rebellion. Four we've marked with asterixes (*) - these are ones where the government has offered a compromise to get them through.

The ailing PM will bid to shore up her position with a crucial address to the backbench 1922 Committee tomorrow night.

She will likely be confronted over her customs 'backstop', which after a Tory revolt she said would end in December 2021 at the latest.

Despite her vow, she has only said she "expects" the backstop, which will continue EU customs rules, to end in 2021.

And today her deputy David Lidington repeatedly refused to rule out the possibility that the backstop won't end on time.

Grilled by the BBC, Mr Lidington only said it was an "intention" and a "hope" that the deal would end by Mrs May's deadline.

Despite the drama a poll has put the Tories on 44%, seven points ahead of Labour on 37%.

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Much of the rise in Tory support is down to a boost with working-class voters according to YouGov, which surveyed 1,619 British adults on June 4-5.