Boris Johnson yesterday defended his controversial plan to allow ministers to tear up the Brexit divorce deal by suggesting the European Union was being unreasonable and failing to negotiate in good faith.
The Prime Minister insisted the legislation, which would put the UK in breach of international law by breaking the terms of the treaty signed with Brussels, was a necessary "legal safety net" to protect the relationship between Britain and Northern Ireland.
As he sought to quell a growing Tory revolt over the measures, he claimed that passing the legislation would strengthen the hand of negotiators trying to strike a trade deal with the EU.
In an effort to reassure Conservative MPs, Mr Johnson said the measures contained in the Bill to set aside parts of the Brexit deal were an "insurance policy" that he hoped would "never be invoked" if an agreement was reached with Brussels.
And he promised that if it was necessary for the powers to be used, MPs would be given a vote on the regulations.
The Internal Market Bill sets out the way that trade within the UK will work once outside the EU's single market and customs union.
Yesterday Tanaiste Leo Varadkar said that if the proposed legislation was a negotiating tactic, it had backfired. And if it was not a tactic, then it meant the UK was a country that doesn't honour international treaties.
It would be "a great shame" for "a really great country to become a shadow of its former self", he said.
All the living former Prime Ministers have voiced concern over the potential breach of international law, while ex-Attorney General Geoffrey Cox and former Chancellor Sajid Javid have added to high-profile Conservative criticism.
Mr Johnson, taking the unusual step of opening the debate on the legislation in the Commons, accused the EU of going to "extreme and unreasonable lengths" over the Northern Ireland Protocol, which he said could lead to "blockading food and agriculture transports within our own country".
The measures, contained in the deal negotiated and championed by the Prime Minister last year, were designed to prevent a hard border on the island of Ireland by keeping Northern Ireland closely aligned with EU customs rules.
The Prime Minister told MPs: "In recent months the EU has suggested that it is willing to go to extreme and unreasonable lengths using the Northern Ireland Protocol in a way that goes well beyond common sense simply to exert leverage against the UK in our negotiations for a free trade agreement."
He warned that the EU could seek to act in other "absurd ways", slapping tariffs on trade between Britain and Northern Ireland.
Mr Johnson said that "if they fail to negotiate in good faith" the UK must introduce a "package of protective powers".
In Stormont First Minister Arlene Foster accused the EU of treating Northern Ireland as its plaything. She said her hope is the contention around the protocol can be removed with the striking of a comprehensive zero-tariff free trade agreement between the UK and EU.
As Northern Ireland would effectively remain part of the single market for goods under the terms of the protocol, the UK Government has claimed the EU is essentially threatening to blockade its goods from entering the region. That contention has been rubbished by senior figures across the EU.
Speaking about the issue in the Assembly, Mrs Foster said: "The EU needs to stop using Northern Ireland to get their own way. We are not the plaything of the European Union and it causes great difficulties here in Northern Ireland when people use Northern Ireland in that fashion."