Prime Minister Theresa May's Conservative government set out its plans on Thursday for a "Great Repeal Bill" to incorporate EU law into British law and "end the supremacy of EU lawmakers" after Britain leaves the European Union.
The government white paper "lays out a pragmatic and principled approach to converting EU law into UK law on the day we leave the EU — giving businesses, workers and investors as much certainty as possible," Brexit Secretary David Davis told parliament.
"It also means the negotiation over our future economic partnership with the EU will be unlike any other in history, because we will start from a point of exact equivalence," Davis said.
"After that, it will be for parliament to determine what EU legislation it wants to amend, repeal or improve — finally ending the supremacy of EU lawmakers," he said.
The white paper was published one day after May formally notified Brussels of Britain's intention to leave the EU, in a letter triggering two years of Brexit negotiations.
Ahead of the publication, the library of the House of Commons, parliament's elected lower house, warned that assimilating EU law into British law was "potentially one of the largest legislative projects ever undertaken in the UK."
The parliamentary library estimated that more than 13 per cent of primary and secondary legislation enacted in Britain between 1993 and 2004 is EU-related.
The London-based Institute for Government said up to 15 more bills could be required to complete the transition, warning that "Brexit will place a huge burden on both parliament and government departments."
Amnesty International, Liberty UK and other human rights and trade union groups have raised concerns that some rights could be eroded in the legal transition.
Catherine Barnard, professor of EU law at the University of Cambridge, said the Great Repeal Bill will represent "an enormous shift of power from parliament to the executive, and one parliament will need to agree to with care."
"In some areas, such as immigration and customs, there will need to be primary legislation since individuals' rights are being affected," Barnard wrote in an analysis for the website UK in a Changing Europe.
Frances O'Grady, head of the Trades Union Congress, said the Great Repeal Bill is May's "chance to make good on her promise to fully protect and maintain all workers' rights that come from the EU."
"These are rights we all rely on – like rules to guarantee safe workplaces, equal pay for women, protection from excessive working hours, and rights to equal treatment for agency workers," O'Grady said.
"The TUC will be watching closely to make sure that every workplace right that comes from the EU is protected – now and into the future."
George Wilson of Liberty UK said the white paper heralds "the biggest shake-up of our laws in generations."
"Our concern is that the Government could use this tumultuous negotiating period to undermine our rights and freedoms," Wilson said.
"The British public voted to leave the EU – not to abandon their rights," he said.