Boris Johnson’s plan to break international law over Brexit has been overwhelmingly rejected by the House of Lords.

Peers voted by 433 to 165 to strip out clauses in the Internal Market Bill which would allow the UK to renege on its obligations in the withdrawal agreement signed with the EU.

The defeat, one of the largest of any government in the Lords since hereditary peers were slimmed down in the 1990s, means that Johnson will have to weigh up whether to reinsert the clause in the House of Commons next month.

In another overwhelming show of strength, the Lords also voted by 407 to 148 to remove any breach of the northern Ireland protocol in the EU withdrawal treaty.

The PM risks a fresh backlash from Joe Biden if he pushes ahead with his proposals, as the president-elect has made plain he believes the British plan poses a threat to the Good Friday Agreement that has kept the peace in northern Ireland for decades.

Speaking after the votes, Labour’s Lords leader Baroness Smith said: “I am sure some in government will initially react with bravado and try to dismiss tonight’s historic votes in the Lords.

“To do so, however, would underestimate the genuine and serious concerns across the UK and beyond about ministers putting themselves above and beyond the rule of law.

“The government should see sense, accept the removal of these offending clauses, and start to rebuild our international reputation.”

Europe minister Lord True said that the vote appeared to be a “wrecking” move and a government spokesperson stressed after the defeat that it was not backing down.

“We are disappointed that the House of Lords has voted to remove clauses from the UK Internal Market Bill, which was backed in the House of Commons by 340 votes to 256 and delivers on a clear Conservative manifesto commitment. We will retable these clauses when the Bill returns to the Commons,” they said.

“We’ve been consistently clear that the clauses represent a legal safety net to protect the integrity of the UK’s internal market and the huge gains of the peace process.

“We expect the House of Lords to recognise that we have an obligation to the people of Northern Ireland to make sure they continue to have unfettered access to the UK under all circumstances.”

During the debate, Conservative former leader Lord Howard had led the calls for Johnson to “think again”, warning the government used the language of “lawbreakers” everywhere.

Howard said “nothing has changed” since Northern Ireland secretary Brandon Lewis admitted the Bill breaks international law in a “very specific and limited way”.

The Brexiteer peer said: “How can we reproach other countries – Russia, China, Iran – if their behaviour becomes reprehensible when we ourselves have such scant regard for the treaties we sign up to, when we ourselves set such a lamentable example?”

Independent crossbench peer Lord Judge, a former head of the judiciary, had advised the House of Lords should be “neither complicit nor supine” and should vote against clauses in the bill.

In a speech on Monday night, former Tory PM Sir John Major also said the bill had already “damaged our reputation around the world”.

Major, who warned Johnson that a second independence referendum in Scotland and a border poll in Ulster were now likely, added that Brexit had meant that Britain is “no longer a great power” and “will never be so again”.

“Suddenly, we are no longer an irreplaceable bridge between Europe and America. We are now less relevant to them both,” he said.

Downing Street will be hoping that its provisions for breaking international law will not be needed if a deal can be struck with Brussels on a trade deal later this month.

The EU has already threatened legal action on the provisions and reintroducing the clause in early December, when the bill returns to the Commons, would be seen as provocative.

Johnson introduced the clauses to the internal market bill because he claimed the EU was planning to interpret the Brexit withdrawal treaty – and its the “northern Ireland protocol” — in an “extreme” way.

He suggested the rules could create a hard border in the Irish Sea, between the province and the rest of the UK.

The legislation aims to limit the EU’s powers to determine state aid for northern Irish firms and customs arrangements in the region.

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