The Brexit deal signed in December has been thrown into jeopardy because of the recent breakdown of relations with the EU, an influential House of Lords committee is warning. The European Union committee says “the threat of no deal remains”, with the European parliament now declining to set a date for its vote on the trade agreement sealed on Christmas Eve. Its chairman, Lord Kinnoull, said there were “noises” coming out of the EU that it might delay ratification beyond the current target of 30 April, risking a further escalation of the row over the deal signed less than three months ago. The peers’ warnings, in a report to be published on Monday, come just days after Brussels launched legal action against the UK, and the European commission vice-president Maroš Šefčovič accused the foreign secretary, Dominic Raab, of displaying a “total misunderstanding” of the Brexit deal. While the UK has exited the EU, the trade deal is only operational because of an emergency procedure on the EU side, with ratification by the European parliament due by 30 April to make it permanently legally binding. While no one expects the deal to be ripped up, the peers, including the former chancellor Lord Lamont and the former national security adviser Lord Ricketts, say the disputes over Northern Ireland “reflect and compound a broader breakdown of trust between the UK government and the EU”. “The European Union committee warned in December 2017 that it was difficult to envisage a worse outcome for the UK than a ‘no-deal’ Brexit. We are therefore concerned that recent developments have so undermined trust that the possibility of ‘no deal’ – in other words, a failure to ratify the trade and cooperation agreement (TCA) – has now resurfaced,” says the report. Beyond Brexit, the Institutional Framework, is the final publication in the 45-year history of the Lords EU select committee, which is now shutting up shop, mirroring the fate of the House of Commons Brexit select committee, which was axed earlier this year. Next week sub-committees will publish five reports on Brexit as a parting shot. They will raise concerns about the delays in setting up governance structures, including 24 specialist committees. The fact they have not been set up yet means “at least 24 pipelines for discussion with the EU are not open” to build post-Brexit working relations in Brussels, according to Kinnoull. On Northern Ireland he said he was “optimistic” the protocol could work but that he was particularly concerned that the joint consultative working group (JCWG) on the protocol was not up and running 14 months after it was mandated. It was supposed to act as the “workhorse forum” for the protocol and had it been put in place last year could have averted the present disputes, he said. The Cabinet Office minister, Michael Gove, recently wrote to him to reveal the JCWG had “convened briefly for the first time” on 29 January “to adopt its rules of procedure”. But its co-chairs and its members are yet to be confirmed. Kinnoull has written to David Frost posing 10 questions about the committee in an effort to increase the pressure. The committee urges both the UK and the EU to reset their relationship. “It is incumbent on both sides to approach the new relationship constructively, in good faith, with the aim of rebuilding trust,” it says. Kinnoull also urged the government to be more transparent about its decisions, saying it was “unhelpful” not to give detailed reasoning behind the recent unilateral decisions over Northern Ireland to match the lengthy letter from the EU outlining its reasons for legal action. “If you are an average MEP and all you are reading is the British government has taken a unilateral action … you have nothing to assess whether the UK was right or wrong.” The committee notes Gove’s recent analogy suggesting Brexit was like the bumpy start of a plane journey which had not yet reached the “gin and tonic” stage, but says it behoves both sides to reset relations. “Liberal democracies are precious, and they should work together, not pull apart,” it says. A government spokesperson said it expected the EU to complete the ratification process as planned by the end of April “to provide certainty to business and individuals on both sides”. On the dispute over Northern Ireland they said the measures taken were “temporary operational steps intended to minimise disruption and protect the everyday lives of the people living there”, adding that “the EU needs to take a more pragmatic approach”.