Brexit vote in Commons could be delayed in extraordinary move by MPs to prevent risk of no-deal

If crucial amendment passes, MPs will only be able to ‘consider the matter’ – not approve the deal

Boris Johnson’s hopes of finally obtaining parliament’s consent on Saturday for a historic deal to take the UK out of the European Union look set to be thwarted by an extraordinary bid by MPs to delay the crucial “meaningful vote”.

Ahead of the highly unusual weekend sitting of the Commons, the prime minister was pulling out all the stops to secure the 320 votes he needs to claim victory in what was expected to be a razor-edge ballot, with the balance held by wavering Labour MPs, hardline ERG “Spartans” and expelled Tory rebels.

But an amendment to his motion tabled by exiled Conservative Oliver Letwin threatens to withhold MPs’ approval until the full legislation to implement the deal is put into law.

With Labour expected to back the amendment, it seems almost certain to pass, after being selected for debate by Commons speaker John Bercow.

The move – designed to avoid no-deal Brexit if the legislation is amended by Brexiteers or fails to complete its passage through parliament by Halloween – would force Mr Johnson to request an extension from Brussels beyond 31 October and could delay the meaningful vote for weeks.

Downing Street indicated it could try to pull back from Mr Johnson’s motion if Letwin's amendment passes, which would deny him the chance to claim he has parliament’s support for the last-minute deal struck with EU leaders on Thursday.

And if the motion fails, he could then face a non-binding vote on a second referendum put forward by Labour backbenchers Peter Kyle and Phil Wilson with the aim of demonstrating that a majority in the Commons back a public ballot on any future change to the relationship between the UK and EU.

The drama came as the result of the vote – if it is held – remained impossible to call, with No 10 buoyed by winning over some Labour rebels while whittling down opposition in its own ranks.

Up to nine Labour MPs are now expected to vote with the Conservatives, after Ronnie Campbell, Sarah Champion and Melanie Onn – who all represent Leave-backing seats – spoke out.

With at least 12 Tory opponents of Theresa May’s deal announcing they would swing behind the prime minister’s reworked version, his chances of victory were growing.

Johnson made a last-minute effort to lure Labour MPs with a set of concessions on workplace and environmental safeguards announced late on Friday night.

But the package - including a promise that ministers will report to parliament on whether the UK will match future EU employment regulations and a pledge not to open UK markets to countries with low environmental and animal welfare standards - was dismissed by Labour’s Laura Pidcock as an “empty gesture not worth the paper it’s written on”.

Labour was locked in a civil war over the punishment to be meted out to its rebels, with Momentum founder Jon Lansman demanding they be expelled, while Jeremy Corbyn insisted they would not.

The Letwin amendment has been tabled to close a loophole in the Benn Act, designed to ensure Mr Johnson must seek to delay Brexit if a deal has not been approved by 11pm on Saturday.

The loophole would allow the prime minister to escape the commitment of seeking a delay if the vote on his deal passes, even though a full withdrawal agreement bill is also needed to ratify the deal – leaving the UK open the risk of a crash-out on 31 October if the bill failed to pass in time.

A furious government source described the amendment as something that “looks as reasonable as possible, but is designed to frustrate the process”.

Joe Owen, Brexit programme director at the Institute for Government, told The Independent: “If the Letwin amendment passes, MPs will only have considered the matter, they will not have approved the deal.”

Crucially, because the Benn Act would not have been satisfied, Mr Johnson would have to request an Article 50 extension – breaking his pledge to lie “dead in a ditch” rather than do so.

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It is also possible that Mr Johnson would be barred from another attempt to stage a “meaningful vote”, forcing him to move directly to the weighty withdrawal agreement bill.

There are certain to be a blizzard of amendments, including for a Final Say referendum, and the bill will take several weeks to pass, going beyond the 31 October scheduled departure date.

But Sir Oliver played down the implications of his amendment, insisting MPs would still have the opportunity to “show in principle they are in favour” of the deal – which he himself supports.

He described it as an “insurance policy which means, if something goes wrong with the legislation, then we ensure the country will still be in the EU after 31 October”.

The government source insisted the vote would still go ahead, even if the Letwin amendment succeeds.