Remain and leave factions in Westminster are working hard to tip the balance of power in their favour

Theresa May’s mission on her whistle-stop tour round the country is clear: tell everybody she meets that the UK would remain “strong and united” after Brexit.

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The prime minister believes that beyond the deep schisms at Westminster, the country just wants to get on with it. Her problem is that the success of that comes down to parliament.

With the clock ticking down to Brexit Day on 29 March next year the government is coming perilously close to running out of time.

While officials on both sides of the Channel are gearing up for formal talks in the next few weeks on the future relationship, MPs and peers are also flexing their muscles.

The key moment comes in October, when the European Union agrees what the deal will look like. After that, parliament gets two votes – on the withdrawal treaty and a political agreement on future relations.



But delivering that “meaningful vote” could come down to the wire. There are already rumours in Whitehall that it could be pushed back to January 2019, leaving parliament and MEPs barely enough time to ratify it.



At that point the EU will take soundings on whether to extend the transition period – which would be met with fury from Brexiters – in order to allow more time.

The “meaningful vote” is the moment of maximum political danger for the prime minister, and her whips are already working round the clock to get Tory MPs into line.

The so-called Brexit ultras are ready to cause trouble, with their leader, Jacob Rees-Mogg, hinting this week that May could be ousted if she fails to deliver their red lines. The motion is expected to be as vague as No 10 can get away with.

Within the cabinet Boris Johnson and Michael Gove are their standard bearers, balanced out by the rather more pragmatic approach of the Brexit secretary, David Davis.

But the most significant group that May needs to win over are the pro-remain Tory MPs, on whom the success of the Brexit project largely depends. While the DUP delivers her a majority, she can’t afford too many of her own rebelling.

Their unofficial leaders are Anna Soubry, the former business minister, and Dominic Grieve, the former attorney general, but they also include the Treasury select committee chair, Nicky Morgan, and arch-Europhile Ken Clarke in their ranks.

Together, the 11 Tory backbenchers, supported privately – though not in the voting lobbies – by some in the cabinet, inflicted a humiliating Commons defeat on the prime minister before Christmas, winning the right to a “meaningful vote” by a majority of just four.

Their next test is likely to be a vote on a customs union, which could come attached to one of two government trade bills. Soubry has tabled an amendment to one and already has the backing of several MPs who share her “naughty corner”.

But these bills are currently in limbo, with the government kicking them down the line until after the May elections, and possibly beyond.

The House of Lords, however, is expected to vote overwhelmingly in support of a new cross-party amendment on the customs union after Easter, so the MPs could still get their chance.

The remain lobby is confident of a Commons majority on a customs union now that Labour has come on board. Tory rebels think their own number could swell slightly. It spells trouble for the prime minister unless she compromises.

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They hope May, who appears to have taken a more pragmatic approach since her Mansion House speech, could be persuaded to face down her Brexit ultras and bring on board the “submarine remainers” – the majority of Tory MPs who voted to stay but are loyal to the party whip.

The final vote is more problematic. Whips are already warning potential Tory rebels that voting against the prime minister could end up ushering in a Jeremy Corbyn-led government. “That’s a risk that some of us would struggle to take, but ultimately this will be our only chance,” one MP said.

Labour faces problems of its own. The shadow Brexit secretary, Keir Starmer, was forced to reassure anxious Labour MPs on Wednesday night that the shadow cabinet was prepared to vote against the final deal after Emily Thornberry, the shadow foreign secretary, suggested it might be so vague her party might back it.

While almost all Labour MPs backed remain, a sizeable chunk of those with Brexit-supporting northern seats - so-called “conflicted labour” – have kept quiet since. Some have even warned against trying to “wriggle out” of Brexit with Europe minister Caroline Flint among those who have defied the party whip.

But it is the small band of Labour Brexiters who will play the biggest role. While two – Kate Hoey and Frank Field – have consistently walked through the Government lobbies, others have not.

Remain supporters still cherish the image of veteran leftwinger Dennis Skinner steering Ronnie Campbell though the lobby to vote for the “meaningful vote”.

Whips persuaded the Labour leavers that their vote would make the difference in defeating the government. “It was too much for them to resist, and we think we could persuade them again,” said one Labour whip.

The remain cause has bound together MPs across party lines, with Labour’s Chuka Umunna and Soubry co-chairing the all-party group on EU relations and working behind the scenes to reassure MPs.

Both the “remain till I die-ers” led by Umunna, some calling for a second referendum, and the single marketeers on the Labour backbenches are pushing the party leadership to go even further.

Corbyn’s long-standing Euro-scepticism, with its concerns over state aid and freedom of movement, suggests this is unlikely, though some believe the whiff of power might help persuade him. “If he thinks that it will make the difference at the next election, who knows how far we’ll go,” said one normally loyal backbencher.

Ministers say publicly they don’t expect a rebellion on the final vote – but they’re still ready.

At an event on Wednesday night Davis vowed not to let the result get in the way of Brexit, declaring that if MPs voted against the final deal “we leave without it”.



But there are moves afoot to make sure remain MPs are not left with Hobson’s choice of backing Brexit or crashing out of the EU.

The Guardian has learned that peers have laid a new amendment that will give MPs a proper say in what happens in the event of them voting down the deal.



There are words of warning from Brussels. One senior EU source suggested MPs were living in “fantasy land” if they thought they could then demand that the government go back to negotiating table. But remain MPs are determined. “We’re not giving up. It’s now or never.”