Theresa May has been accused of a sweeping “power grab” after unveiling plans granting her ministers the ability to rewrite reams of British law without full scrutiny.

The move to adopt so-called “Henry VIII” powers was slammed by opposition politicians, with those in England and Scotland vowing to derail Ms May’s legislative programme unless safeguards are introduced.

Gina Miller, who defeated Ms May at the Supreme Court over Article 50, said she could launch a new challenge over the issue, while campaigners claimed the powers could see the Tories strip back protections on anything from human rights to wildlife and the environment.

Even business leaders raised concerns that the powers, allowing ministers to wave through laws without full scrutiny, could lead to sudden changes that leave firms facing costly legal battles.

Cabinet minister David Davis revealed the Government could tamper with up to 1,000 pieces of smaller legislation and will also introduce a raft of other acts of parliament – including on immigration and the customs union – in order to make Brexit a reality.

The Brexit Secretary said: “These steps are crucial to implementing the result of the referendum in the national interest. I hope all sides will recognise that, and work with us to achieve these aims.”

The prospect of “Henry VIII” powers, so named because they date back to the reign of the autocratic ruler, was raised by the Government’s planning paper for its Great Repeal Bill – Ms May’s key of piece legislation enabling Brexit.

It will see every piece of EU law affecting the UK brought onto the UK statute book on the day of Brexit, with ministers then given the powers to adjust parts to make them workable in the UK and potentially ditch parts they do not like.

Anti-Brexit protesters, one wearing a giant Theresa May head, hold placards outside Parliament on the day the Prime Minister will announce that she has triggered the process by which Britain will leave the European Union (Reuters)

But the plan caused an immediate backlash after Mr Davis admitted he did not yet know if the law would need “legislative consent” from the devolved assemblies, something needed for anything affecting their powers.

The SNP’s Nicola Sturgeon indicated it would be “absolutely unacceptable” for powers to be lost from Edinburgh, raising the prospect that the party may seek to block it.

Liberal Democrat Chief Whip Tom Brake said: “Theresa May and her ministers are resembling a medieval court more and more every single day. This shameless power grab under the cloak of secondary legislation would have made Henry VIII blush.

“If needed, we will grind the Government’s agenda to a standstill, unless proper and rigorous safeguards are given over the Great Repeal Bill.”

The Government is particularly vulnerable to resistance in the Lords where Conservatives are outnumbered by Labour and Lib Dem peers.

Shadow Brexit Secretary Sir Keir Starmer pointed out how the planned bill hands “sweeping powers to the executive”.

He added: “In those circumstances one might expect some pretty rigorous safeguards to the use of those sweeping powers, but none are found in the White Paper.”

Brexit Secretary David Davis admits deal with 'exact same benefits' is not a promise

There are currently more than 12,000 EU regulations in force in the UK and a further 8,000 pieces of domestic regulation implementing EU legislation. In addition, House of Commons research indicates that between 1980 and 2009

Some 186 UK acts incorporated a element of EU legislation. All of the related European regulation now needs to be brought in to UK statute book.

Given the sheer amount of legislation than needs to be adopted, the Government argues the powers are needed so the task can be completed before the UK drops out of the EU on 29 March 2019.

But cabinet ministers including Foreign Secretary Boris Johnson and other Conservative MPs have hailed the opportunity to strip away what they call “burdensome regulation”.

Campaigner Ms Miller, who successfully took the Government to court over its plans to trigger Brexit without parliamentary approval, said she was considering legal action to challenge the use of Henry VIII powers to alter individuals' rights.

She said: "If there is any sniff that they are trying to use Henry VIII powers, that would be profoundly unparliamentary and democratic, and I would seek legal advice.”

Politicians have raised fears that workers' rights, like paid holiday or laws limiting working hours, and consumer protections could be trimmed, though ministers insist they will be protected.

Friends of the Earth campaigner Samuel Lowe said the Government must not be able to change the purpose or meaning of laws without proper scrutiny, adding: “Any substantive changes to these laws should be made by primary legislation only.”

Campaigners explained that key pieces of regulation setting out standards on air pollution or protecting endangered species could be affected.

Director of Liberty Martha Spurrier demanded an independent audit of the human rights protections the public stand to lose and a formal commitment that every one of them will be safeguarded.

She said: “Where’s the guarantee to protect our EU rights so we don’t end up worse off than our neighbours across the Channel? Where’s the guarantee of proper democratic scrutiny?”

The British Chambers of Commerce joined the fray, telling the the Government it has to be “exceedingly careful in its use of proposed fast-track powers”, or risk blighting businesses with additional costs and burdens.