Sweeping powers to water down human rights and equalities laws would be handed to the Government by Brexit legislation to be debated this week, MPs have been warned.

Ministers are poised to grab the ability to rewrite the likes of the Equality Act and the Modern Slavery Act at the request of a foreign power, bypassing MPs, civil rights group Liberty said.

The Trade Bill “presents a significant threat to rights” unless the Commons stands firm and requires it to be rewritten, it argued.

“It allows them to change laws that originated from the EU without consulting MPs or the public,” a spokesman said.

“This means they could unilaterally rewrite equalities protections and anti-trafficking laws at the behest of a foreign power who thinks our hard-won rights get in the way of importing and exporting goods.

“MPs must remove this power grab from the Bill or risk handing over our rights and our sovereignty to the highest international bidder.”

The legislation was the latest attempt by ministers to “undermine democracy and bypass parliamentary scrutiny of the Brexit process”, after the flagship EU (Withdrawal) Bill contained similar “Henry VIII” powers, the organisation said.

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Labour said it shared Liberty’s fear, accusing the Government of “taking every opportunity to grab powers that should be restored to Parliament as the United Kingdom leaves the EU”.

“Masquerading as the champion of the people, the Conservatives have tried to erode democracy and to remove any necessary checks and balances on executive power – powers that they intend to use to remove the rights and protections of the very people they claim to represent,” said Barry Gardiner, the Shadow Secretary of State for International Trade.

“It is appalling, which is why Labour has sought to fight this power grab at every step and will do the same with Tuesday’s second reading of the trade bill.”

The Trade Bill, to be given its second reading on Tuesday, is one of several controversial further pieces of Brexit legislation in the pipeline.

Meanwhile, the Taxation (Cross-Border) Bill, being debated on Monday, will allow the Government to establish “a customs union between the UK and the country or territory” – determining the customs arrangement with the EU at the end of the post-Brexit transition period.

This Bill has already caused uproar, because it will force more than 130,000 UK firms to pay VAT upfront on all goods imported from the EU after withdrawal.

Labour and Tory MPs and peers will argue that the only way to avoid the VAT Brexit penalty would be to stay in the customs union, or negotiate to remain in the EU-VAT area.

Ministers say the Trade Bill is required to give the Government maximum flexibility when implementing trade deals but – Liberty has protested – it contains no safeguards to protect rights.

Clause 2 would give ministers unfettered power to amend “retained EU law”, it said – including the Equality Act and Modern Slavery Act – with limited or no parliamentary oversight, it said.

They would be able to pass regulations they consider appropriate “for the purpose of implementing an international trade agreement” including “modifying primary legislation that is retained EU law”.

The Equality Act, passed by Labour in 2010, brought together existing, confusing anti-discrimination laws, to guarantee access to jobs and services regardless of age, gender, disability, race, religion or sexual orientation.

The Modern Slavery Act would ensure prosecution of people “involved in this disgusting trade in human beings”, the Home Office said, in 2015, when led by Theresa May.

Liberty added: “We recognise the importance of the Trade Bill in allowing the UK to shape its own trade and investment agenda once we leave the EU.