Keir Starmer is facing a high-profile rebellion against Labour’s Brexit position on the eve of the vote in parliament, as prominent MPs including John McDonnell and Clive Lewis accused him of “falling into the trap of rallying around this rotten deal”. Labour is likely to contain a major rebellion of frontbench MPs but an increasing number of prominent supporters are urging Starmer to change course. Backbenchers have also raised concerns on private WhatsApp groups that Labour’s endorsement for the deal has been given without the legislation being published. Tory Brexiters who are studying the trade deal will deliver their verdict on Tuesday afternoon. The European Research Group (ERG), the influential group of Eurosceptic backbenchers, will take its cue from its so-called “star chamber”, which includes the ERG deputy chairman David Jones, Sir Bill Cash and the QC Martin Howe, and is scrutinising the deal. It is understood senior members of the ERG are broadly supportive of the document but have identified issues – including fishing rights – where members plan to raise concerns. Those who signed the Labour statement urging Starmer not to support the deal come from across the political spectrum, including the former shadow chancellor McDonnell and Ben Bradshaw, a former cabinet minister who is a staunch supporter of Starmer. “This deal is a substantial downgrade of the UK’s relationship with the EU,” the statement warns, “and is designed to open the door to rampant economic deregulation – a loss of rights and protections for workers, the environment, food standards and many other areas of life.” Two former Labour leaders in the European parliament, Richard Corbett and Glyn Ford, as well as the former MEPs Julie Ward, Mary Honeyball, David Martin and Jude Kirton-Darling have also signed, along with the former Labour cabinet minister Andrew Adonis. The statement, organised by Another Europe is Possible and Labour for a Socialist Europe, has also been endorsed by two former MPs who lost their seats in the 2019 election, Anna Turley and Sandy Martin. Activists including Laura Parker, the former head of Momentum, the film-maker Paul Mason and Michael Chessum, from Another Europe Is Possible, who coordinated leftwing second-referendum efforts under Jeremy Corbyn, have also signed. The group that signed the statement, which also includes local activists and councillors, says the task of the opposition is proper parliamentary scrutiny and setting out an alternative. “That task gets harder if opposition parties fall into the trap of rallying around this rotten deal,” it says. “We are witnessing an act of vandalism against our livelihoods, our rights and our horizons. We call on Labour, the Labour movement and other opposition parties not to support the Tories’ Brexit deal when it is put to a vote in the House of Commons.” The UK parliament has been recalled to sit on Wednesday 30 December to debate and vote on the legislation but MPs are widely expected to pass the post-Brexit trade and security deal by a substantial margin after Starmer confirmed Labour would support it. The Lib Dems and the SNP are to vote against the deal. Any Tory Brexiter rebellion is likely to be small, though most said there would be no “whipping” arrangements for group members. “It will be up to individual colleagues to decide how they vote,” one MP said, a contrast to the heavily coordinated opposition of the Theresa May era. The Democratic Unionist party said it would be voting against the Brexit deal “on a point of principle” and not because it supported no deal, it said. The party’s leader, Arlene Foster, said she recognised it reduced the impact of red tape on trade between Great Britain and Northern Ireland, but “we still have many negative issues” arising from the Northern Ireland protocol. Other Northern Ireland MPs from the SDLP and Alliance parties will also vote against the deal. On Monday EU member states unanimously backed the deal, paving the way for the new arrangements to come into force on 1 January. At a meeting of ambassadors in Brussels, the 27 member states gave their support for the 1,246-page treaty to be “provisionally applied” at the end of the year. The European parliament is delaying its vote until February or March, when it is hoped MEPs will return to Strasbourg to complete the formal EU ratification process. Speaking on Monday morning, the Cabinet Office minister, Michael Gove, hailed the deal but said British businesses faced a “bumpy” period from 1 January. “Businesses will need to make sure that they’re ready for new customs procedures and we as individuals will need to make sure that our passports are up to date because they need to have at least six months before expiry on them in order to be able to travel abroad,” he said. “I’m sure there will be bumpy moments but we are there in order to try to do everything we can to smooth the path.” There has been mounting anger from Britain’s fishers about the extent of EU boats’ fishing rights in UK waters. Under the terms of the agreement, 25% of EU boats’ fishing rights in UK waters will be transferred to the UK fishing fleet over a five-and-a-half-year transition period. Gove said UK fishers would be “getting a significant uptick … we will have by 2026 about two-thirds of the fish in our waters”. However, Andrew Locker, the chairman of the National Federation of Fishermen’s Organisations, said they would be “absolutely worse off” as a result of the deal. “What we have got now is a fraction of what we were promised through Brexit. We are going to really, really struggle this year.” Many MPs on all sides have told whips they do not plan to be present on Wednesday given London’s tier 4 coronavirus restrictions. The Commons Speaker, Lindsay Hoyle, has strongly urged MPs to participate virtually and to use proxy votes.