Prime Minister Boris Johnson was trying to dampen down growing opposition on Monday to his plan to unilaterally rewrite Britain's divorce deal with the European Union, after his former attorney general said doing so would permanently damage the U.K.'s reputation.
Geoffrey Cox, who was the government's top legal officer when Johnson negotiated the agreement less than a year ago, said reneging on the deal would be an ``unconscionable'' breach of international law.
Cox, previously a strong supporter of Johnson on Brexit, said he wouldn't support the proposal when the House of Commons takes its first vote on the contentious legislation later Monday.
``I simply cannot approve or endorse a situation in which we go back on our word, given solemnly,'' Cox said Monday on Times Radio. ``The breaking of the law ultimately leads to very long-term and permanent damage to this country's reputation.''
Johnson's move threatens to sink already-foundering negotiations between Britain and the EU on a post-Brexit trade deal.
As part of the Brexit divorce deal, Britain and the EU agreed to keep Northern Ireland _ the only part of the U.K. to share a border with the bloc _ bound to some EU rules on trade, to avoid the need for border checks on goods moving between Northern Ireland and the Republic of Ireland. Both sides accepted the compromise to protect the open border, which helps underpin the peace process in Northern Ireland.
Johnson claims the EU has threatened to use ``an extreme interpretation'' of the withdrawal agreement to ``blockade'' food shipments from the rest of the U.K. to Northern Ireland unless Britain agrees to accept EU regulations. He says that threatens the integrity of the U.K.
The Internal Market Bill, which the government hopes to pass into law within weeks, would give the British government the power to override the EU's agreed role in oversight of trade between mainland Britain and Northern Ireland.
The EU denies threatening a blockade and says it merely wants Britain to live up to terms of the agreement.
EU leaders are outraged at the prime minister's proposal, which the British government accepts would breach an international treaty.
The bloc has threatened the U.K. with legal action if it does not drop the proposal by the end of the month.
With an 80-seat majority in the House of Commons, Johnson is expected to have enough votes to push his legislation through Parliament. But Cox's opposition reflects wide unease within the governing Conservative Party.
Conservative lawmaker Rehman Chishti quit Monday as the prime minister's special envoy on freedom of religion in protest at the bill. He tweeted that as a former lawyer, ``values of respecting rule of law & honouring one's word are dear to me.''
Cox, a respected lawyer who staunchly defended the government during parliamentary debates on the withdrawal agreement last year, said that the ``unpalatable'' consequences of the withdrawal deal were well-known when it was negotiated.
He said that rather than reneging on its international commitments, the government should use the legal remedies contained in the agreement itself to challenge any unreasonable behavior by the EU.
``No British minister should solemnly undertake to observe treaty obligations with his fingers crossed behind his back,'' Cox wrote in the Times of London.
The debate comes at a crucial moment for talks between Britain and the EU.
The U.K. formally left the bloc on Jan. 31, but existing trade rules remain in effect until the end of this year under a transition arrangement designed to provide time to negotiate a long-term trade agreement.
Despite the chill in relations between London and Brussels and the threat of legal action, trade talks between the two sides are due to continue this week. Both sides say any deal must be agreed by next month so there is time for it to be ratified by Dec. 31.
If there is no deal, tariffs and other impediments to trade will be imposed by both sides at the start of 2021.
That would mean huge economic disruption for the U.K., which does half its trade with the bloc. A no-deal exit on Jan. 1 would also hit some EU nations, including Ireland, France, Belgium and the Netherlands, especially hard.