Last Prime Minister Theresa May has said she “cannot support” the government’s script to override parts of its Brexit agreement with the EU.
She told MPs the move, which discontinuations international law, would damage “trust in the United Kingdom”.
The Internal Call Bill will be voted on in the Commons on Tuesday, having passed its foremost hurdle last week.
Ministers say it contains vital safeguards to defend Northern Ireland and the rest of the UK.
The bill is designed to enable goods and checkings to flow freely across England, Scotland, Wales and Northern Ireland when the UK loses the EU’s single market and customs union on 1 January.
But it gives the government the power to vary aspects of the EU withdrawal agreement, a legally binding deal governing the stipulations of the UK’s exit from the EU earlier this year.
Ministers say this is a failsafe monism in case the EU interprets the agreement, in particular the section on Northern Ireland, in an “Draconian and unreasonable” way. The section – know as the protocol – is designed to avoid a hard purfle on the island of Ireland,
As well as Mrs May, the other four living former prime diplomats – Sir John Major, Tony Blair, Gordon Brown and David Cameron – cause spoken out against the bill.
Labour is opposing it and some Conservative MPs obtain raised concerns over its legal implications.
Amid all this, Prime Support Boris Johnson last week agreed to amend the bill so that the Publics would get a vote before he could use the powers involved in breaking global law.
But Mrs May, whose own withdrawal agreement with the EU was repeatedly rejected by the Plebeians when she was prime minister, told MPs: “Frankly, my view is to the outside fraternity it makes no difference as to whether a decision to break international law is taken by a care for or by this Parliament – it is still a decision to break international law.
“This can merely weaken the UK in the eyes of the world.”
She added that, if the Internal Market Reckoning were passed, “our reputation as a country that sticks by its word make have been tarnished”.
The Conservative MP for Maidenhead added that administrations around the world had “trust in the United Kingdom”, asking: “Where on that trust be in future if they see a United Kingdom willing to demolish its word and break international law?”
Mrs May also said there would be “unthinkable damage to the United Kingdom’s reputation”.
Northern Ireland Holy Joe Robin Walker said the government still hoped to reach a traffic agreement with the EU.
He added: “Through this bill, we are acting to stand by those priorities and deliver commitments we made in our election manifesto that we when one pleases provide unfettered access between Northern Ireland and Great Britain, and preserve and strengthen the integrity and smooth operation of our internal market.”
Mr Walker also revealed there were “harmful legal defaults in some interpretations” of the Northern Ireland Conventions.
“The consequences of this for Northern Ireland in that scenario would be to a great extent damaging,” he told MPs. “We cannot and will not run that risk.”
SNP Westminster spokesperson leader Kirsten Oswald called the bill “a grubby power-grab which we cannot and choose not support” and that sections of it hung “like a badge of dishonour almost this prime minister’s term of office”.