Britain's ministers have been forced to back down on Tuesday after parliament found the government was contempt over an order to publish full legal advice on prime minister Theresa May's Brexit deal with the EU.
In a major blow to the government's Brexit plans, Conservative House leader Andrea Leadsom indicated the legal advice would be published on Wednesday.
Mrs May was due to open five days of parliamentary debate about her Brexit withdrawal deal ahead of a crunch vote billed for December 11.
But the debate was delayed as MPs voted on the contempt motion.
Ms Leadsom had argued that the advice is confidential but opposition party Labour said the government was “wilfully refusing” to comply with an earlier order passed through parliament.
Critics of the government said they suspect the advice will reveal the Attorney General Geoffrey Cox's misgivings about the Brexit agreement.
The contempt row is unlikely to lead to Mrs May’s downfall but the debate highlighted how little trust MPs have in the deal agreed with Brussels.
Earlier on Tuesday a senior adviser to the European Court of Justice said Britain could unilaterally halt its divorce from the European Union.
Advocate General Campos Sanchez-Bordona said he believed Britain could revoke Article 50 without agreement from other EU states.
The ECJ said Article 50 "authorises the unilateral revocation of the notification of the intention to withdraw from the Union".
"That possibility continues to exist until the withdrawal agreement is formally concluded," the court added.
As a result, the British pound rallied, gaining 0.7 per cent against the US dollar to $1.281.
Meanwhile, Bank of England Governor Mark Carney hit back at "unfair" criticism, after pro-Brexit MPs accused him of scaremongering. Last week, the bank said a chaotic exit from the EU could, in a worst-case scenario, lead to the economy shrinking by as much as 8 per cent within a year and house prices plunging by a third.
Mr Carney insisted that there was only a small chance this could happen, but said the bank was duty bound to inform MPs of its analysis.
While Tuesday's legal opinion from Mr Sanchez-Bordona, which is usually but not always followed by judges at the ECJ, gave a boost to the significant number of pro-European MPs who do not want to see Brexit happen at all.
Scottish MEP Alyn Smith who, along with other politicians from a range of parties, launched the legal proceedings in December last year, said the legal opinion showed that the “Brexit clock” could be stopped.
The Scottish National Party politician insisted there was “a road map out of the Brexit shambles”.
"This is a huge win for us, and a huge step forward from the highest court in the business, and confirms what we have been hoping for: that the UK can indeed change its mind on Brexit and revoke Article 50, unilaterally,” he said.
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Article 50 was invoked on March 29 last year, following the June 2016 Brexit referendum. Britain is now due to exit the EU in less than five months.
Mrs May said Britain will leave regardless of any future decision by the EU’s top court and that the choice is between her deal or no deal.
But pro-Europeans in Britain hope that if the ECJ rules that any member state can unilaterally withdraw from Article 50 then a third option – to remain in the bloc – will become even more of a possibility.
The decision is expected to be made by the end of the year, but judges at the ECJ must first accept jurisdiction over the case.