The government has clashed with trade unions over claims that 20 days of statutory holiday and eight bank holidays, along with a “tapestry” of workers’ rights, are at risk under post-Brexit plans to remove EU laws from the UK’s statute books. Shantha David, head of legal services at Unison, told a parliamentary committee examining the retained EU law (revocation and reform) bill that these rights “would no longer survive” if automatically removed via the “sunset clause” that will sweep away EU laws unless they are actively saved by a minister on 31 December 2023. The committee was taking evidence from lawyers, unions, environmentalists and devolved government representatives as it emerged that the National Archives have found another 1,400 laws in addition to the 2,400 the government has already identified as falling within the bill’s scope. David told MPs that she was concerned that laws protecting employees could “disappear overnight” as a consequence of the sunset clause, including parity of pay for workers and paternity leave. “Given the lack of information we have, it’s unclear what will survive and what will face the chop,” she said. Her remarks came after weeks of criticism that the government is operating a “smash and grab” operation to get rid of EU law for ideological rather than best practice purposes. But her claims that the government would guillotine whole swathes of workers’ rights enraged the business minister Nusrat Ghani, who accused her of fearmongering. Ghani told MPs that she “struggled” with David’s analysis. “I’m anxious about this constant speculation and the fear that it’s creating,” she said, before listing a string of rights the UK has led on globally including paternity leave, fines for aggravated breaches of workers’ rights and paid bereavement leave. David hit back by saying the government’s dashboard listing the EU laws that were in scope was “the most incomprehensible piece of equipment” for people to understand what laws the government was taking aim at. Tim Sharpe, senior policy officer for employment rights at the Trades Union Congress, said it was “great news for bad bosses”. In a second confrontation with the union leaders, it was left to the Conservative backbenchers Marcus Fysh and David Jones, prominent Eurosceptics, to give the government assurances they were seeking. “I’m quite sure that the government and its ministers will be very keen to make sure that people’s rights are preserved. I can’t personally imagine a scenario in which they wouldn’t be very careful about those things,” said Fysh. “There is no way the government would scrap these rights you are talking about,” added Jones. The committee was taking evidence from experts and stakeholders as part of a consultation process after the second reading of the bill, first tabled by the former business secretary Jacob Rees-Mogg in September. Ghani also clashed with environmental groups, who said they had been led to believe there were 835 laws that could be switched off by the bill, significantly more than the 570 cited on the government’s dashboard. Richard Benwell, chief executive of the Wildlife and Countryside Link, called on the government to withdraw the bill, claiming it was faulty and “irredeemable”. Ghani questioned the neutrality of his evidence, saying he was a Lib Dem who had campaigned for public office. But Ruth Chambers, a senior fellow at the Green Alliance, said she agreed with Benwell. It was not that environmental groups objected to laws being changed, she said, but the mass removal the government was planning. Earlier the committee heard from a string of eminent lawyers, some of whom supported the bill including Martin Howe KC and Tom Sharpe KC, who said they had faith the government would do the right thing. Retired judge Sir Richard Aikens, a former lord justice of appeal, said the law was an “invitation to appeal” and an “invitation to litigate” by those seeking to protect workers rights. Earlier on Tuesday, the Scottish government lodged a legislative consent memorandum recommending that the Holyrood parliament withhold its consent for the bill. The Welsh government did this last week, when the counsel general for Wales, Mick Antoniw, described as “constitutionally unacceptable” the clauses allowing UK ministers to act in devolved policy areas without the consent of the devolved administration. In a letter to Grant Shapps, Scotland’s constitution secretary, Angus Robertson, echoed this concern, warning that the bill represents “a significant further undermining of devolution”, adding that the speed at which the legislation is being pursued is “nothing short of reckless”. Both Scottish and Welsh ministers point out that, while the bill includes an extension mechanism for the sunset date until 2026, the exercise of this power is limited to UK government ministers. David Bowles, head of public affairs and campaigns at the RSPCA, said he was concerned that of the 44 laws governing animal welfare protection, 31 were “probably devolved”. Aikens said it was “an almost impossible task” to review 2,400 laws by next December and he was “pessimistic” it could even be done by 2026, an alternative date within the bill. More generally, he predicted that judges would approach cases very conservatively and be reluctant to tread into areas of public policy.