Senior ministers in the Welsh and Scottish governments have furiously criticised “last-minute and cack-handed” plans from the Conservatives to scrap or amend thousands of EU rules. The move – nicknamed the “Brexit freedoms bill” – has also raised alarm from constitutional experts who said it would make it easier for ministers to bulldoze through important parliamentary scrutiny. Senior sources in the devolved governments have accused the UK government of failing to properly consult ministers in Edinburgh, Cardiff and Stormont, even though the proposals, released on Monday by No 10, will have a significant impact on hundreds of areas controlled by devolved governments. One source said the Welsh, Scottish and Northern Irish parliaments first learned an announcement was imminent when they were invited at 1.51pm last Friday to an unexpected meeting on Saturday with Suella Braverman, the attorney general. It involved ministers from all three devolved administrations and the cabinet ministers for Scotland, Wales and Northern Ireland. The source said Braverman was badly briefed and was unable to provide full answers to questions the Scottish government asked, even though the proposals had a direct impact on Scottish law and policy. “There were no meaningful answers at all,” said one source. Another said the meeting was “last-minute, fractious, and cack-handed”. Hannah White, the deputy director of the Institute for Government, said MPs needed to closely scrutinise the scope of ministers’ powers to change retained EU law without primary legislation. “Allowing ministers to repeal or modify fundamental rights embodied in retained EU law without full parliamentary scrutiny would be wrong,” she told the Guardian. Dr Ronan Cormacain, a senior research fellow at the Bingham Centre for the Rule of Law, said the proposal “appears to be proposing a system to change EU law which bypasses parliament. Under the guise of taking back control, it would appear that the executive is taking away control from parliament and giving it to ministers. “There is nothing wrong with making new laws that deviate from the EU. There is everything wrong with bypassing parliament to do so.” The devolved governments suspect the rushed launch of the proposals suggest UK government departments are under intense pressure to announce major policies to deflect attention from the “partygate” crisis threatening Boris Johnson’s premiership. Mick Antoniw, the Welsh government’s constitution minister, was described as furious. He said after the meeting the proposals would “drive a coach and horses through the concept of mutual consent”. There was no effort by the UK government to properly consult devolved governments on the details of the plans nor seek their views on their impacts on devolved areas of policy and law. Angus Robertson, the Scottish constitution affairs secretary, said the mishandling raised profound doubts about Boris Johnson’s pledge earlier in January to promote “mutual respect, maintaining trust and positive working” between the four governments, as part of a new ministerial council the prime minister would chair. Johnson’s initiative, instigated by Michael Gove, the UK minister for intergovernmental relations, followed increasingly angry complaints the UK government has failed to consult devolved leaders or to respect their independent policymaking over Brexit and its impacts, including reforms of the UK’s internal market. “Within days of the UK government promising more respectful ways of working, we were informed of what is clearly a rushed exercise over the weekend with nothing more than a vague verbal briefing,” Robertson said. “If these proposals involve changing the law in devolved policy areas, then pressing ahead without the consent of the Scottish parliament would demonstrate yet again the UK government’s intent to undermine devolution.” The areas affected by the proposed bill, which has yet to be published, include climate policy, agricultural rules, food safety, genetic modification, vehicle safety and industrial subsidies. Many of these areas are directly controlled by devolved parliaments. A UK government source said the devolved administrations’ criticisms were unjustified; meetings in government were often arranged at short notice. “They have been brought in at an early opportunity. That’s actually part of constructive engagement,” he said. “If they’d just read about it in the Sunday papers, they would’ve had a leg to stand on.”