British Prime Minister Boris Johnson will try to persuade rebellious lawmakers in his party to vote on Monday for a bill that would break international law by breaching parts of the Brexit divorce deal and that Brussels says will wreck trade talks.
The House of Commons will debate the Internal Market Bill, which the EU has demanded Johnson scrap by the end of September, in the latest brinkmanship of a four-year saga since Britain voted narrowly to leave the bloc.
After the debate, in a vote that may come late, lawmakers will decide if the bill should go to the next stage.
Johnson's plan to explicitly break international law has plunged Brexit back into crisis less than four months before Britain is finally due to leave the EU's orbit at the end of a transition period, and jeopardised trade talks.
EU diplomats and officials said the bloc could take legal action against Britain, though there would be no resolution before the end-of-year deadline for its full exit.
The EU has ramped up preparations for a no-deal Brexit, which would be chaotic for business, markets and nearly $1 trillion in annual trade.
Johnson, who has a majority of 80 in the lower house of parliament, faces a growing revolt. All of Britain's living former prime ministers have expressed concern about his plan as have many senior figures in his Conservative Party.
"No British minister should solemnly undertake to observe treaty obligations with his fingers crossed behind his back," Johnson's former Attorney General Geoffrey Cox, who is influential with colleagues, said in The Times newspaper.
Conservative lawmaker Rehman Chishti, who was Johnson's special envoy for freedom of religion, quit his role, saying he could not support the bill. "As an MP (lawmaker) for 10yrs & former Barrister, values of respecting rule of law & honouring one's word are dear to me," he tweeted.
WHO BLINKS FIRST?
British ministers say the bill, which explicitly states that it could be inconsistent with a host of international laws, is intended to clarify ambiguities - particularly over Northern Ireland - and act as a safeguard in case trade talks fall.
But some EU diplomats believe London is playing a game of chicken, inviting the collapse of trade talks to either get the deal it wants or leave without a deal.
The EU says it cannot trust those who break agreements and that if the bill is not effectively scrapped there will be no trade deal to cover everything from car parts to food.
The pound fell 3 percent last week on fears of a no-deal Brexit.
Irish Foreign Minister Simon Coveney said the bill was most likely a tactic and a "thin" free-trade deal was still possible as there were just a few outstanding issues.
If, as expected, it is passed in its second reading on Monday, there will be four more days of debate on the bill's fine print - lasting into Tuesday of next week.
If the bill passes the lower house, it will undergo scrutiny in the House of Lords where opposition from Conservative members is expected to be even stronger.