MPs could still alter any Brexit deal secured by Theresa May and voted through by a majority in parliament, researchers have concluded.

Analysis of parliamentary procedures on both sides of the Channel show that MPs could wave Brexit through but still force concessions during the process of putting it on the statute books. They could also make amendments to the withdrawal bill, which could amount to a rejection of the deal.

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It is widely expected that if May gets a deal she will leave as little time as possible for MPs to scrutinise it, calling a vote in the House of Commons within days of returning from Brussels. However, the researchers said this could prove problematic.

“If MPs feel they have been press-ganged into voting on a deal that they have not had sufficient time to absorb, this could create problems down the line,” said the authors of The Brexit Endgame, published on Saturday to mark the start of the six-month countdown to the departure deadline.

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The report – written by researchers from the UK in a Changing Europe organisation, which conducts academic research on Brexit, and the Bingham Centre for the Rule of Law – shows that even if the prime minister secures a deal, she is not home and dry.

The authors, Matt Bevington, Alan Wager and Jack Simson Caird, spell out the hurdles she must jump, testing every permutation of parliamentary procedure.

If May strikes a deal with Brussels, she will come back with two settlements: a fully agreed draft withdrawal bill, which must then be made into law; and a political deal, which will set the framework for the future relationship and trade negotiations between the UK and the EU.

The authors point out that if politicians vote through the deal, they will still have the option to make amendments to the withdrawal agreement when it is translated into a bill. Anything substantial would amount to a rejection, which is is unlikely, but they could win concessions at this point.

“MPs will have longer to scrutinise [the bill] than the withdrawal agreement so it is therefore conceivable that they will raise issues at this point that they did not have time to bring up or had not considered when the exit deals were passed,” they say.

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MPs could make their support conditional on a vote on the final trade deal, or on a second referendum.

“As we’ve seen with previous bits of Brexit-related legislation, the threat of a defeat might lead the government to amend its proposals,” the report says.

If the government rejected any proposed amendments, it could offer inducements instead, such as a “meaningful vote” on the trade treaty.

The political agreement that May hopes to secure in Brussels is not legally binding so a meaningful vote on the future trade deal could be valuable to her opponents.

Alternatively, the government could choose not to resubmit the deal for parliamentary approval and simply end the negotiations and opt for a no-deal scenario.

Under its own rules, the government must make a statement by 29 January on what it intends to do. If there is no agreement, the authors believe this would be the point when a vote of no confidence could occur under the Fixed Term Parliaments Act. This does not automatically trigger a general election but would make one more likely.

The authors’ analysis of the unprecedented European procedures also highlights the potential for changes in the unlikely event that the European parliament rejected the deal. If it did, EU negotiators would have to seek changes to the withdrawal agreement to satisfy the European parliament.

If negotiations on either side took a little longer than timetabled and the article 50 process was extended slightly, the pressure to sign off would still be immense, the authors predict.

The European parliament’s last voting session is on 18 April. If a deal is not ratified by then, Brexit could not be voted on again until parliament returned in the autumn and a much longer extension of article 50 would have to be considered. This would require unanimous support at the European council of prime ministers.