The European Union's top court has ruled Britain can change its mind over Brexit, boosting the hopes of people who want to stay in the EU that the process can be reversed.

Key points: The court said there would be no penalties to the UK for reversing the deal

The court said there would be no penalties to the UK for reversing the deal It was believed most EU members would have to agree on UK reversing Brexit

It was believed most EU members would have to agree on UK reversing Brexit There are reports that Britain's PM has called an emergency meeting and has decided to pull out of tomorrow's Parliamentary vote on the Brexit deal

In an emergency judgement delivered just a day before British Parliament is due to vote on the Brexit deal agreed with the EU, the European Court of Justice (ECJ) ruled that when an EU member country has notified its intent to leave, "that member state is free to revoke unilaterally that notification" without consulting other member states.

The ECJ said in its statement that Britain should suffer no penalties if it halted the Article 50 process.

"Such a revocation, decided in accordance with its own national constitutional requirements, would have the effect that the United Kingdom remains in the EU under terms that are unchanged."

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Following the ECJ decision, local media reported that British Prime Minister Theresa May had called an emergency meeting with senior aides and ministers to discuss the idea of pulling or postponing the vote.

The BBC and other outlets reported the Government decided it would postpone the scheduled vote, with two sources telling BBC political editor Laura Kuenssberg it was being pulled.

But Mrs May and her ministers had repeatedly insisted the vote would go ahead as planned, and her spokeswoman briefed reporters earlier on Monday that there was no plan to pull it.

Mrs May is set to make a previously unscheduled statement at 3:30pm (local time). If the vote is delayed, it would set up further tense talks with the EU when she goes to Brussels on Thursday for a summit of national leaders.

But in pre-empting the possibility of further negotiations, an EU spokeswoman said the executive would not renegotiate its Brexit agreement, adding the bloc was ready for "all scenarios".

'There is a way out of this mess'

Britain voted in 2016 to leave the 28-nation bloc, and invoked Article 50 of the EU's Lisbon Treaty in March 2017, triggering a two-year exit process.

As Article 50 contains few details — in part because the idea of any country leaving was considered unlikely — a group of Scottish legislators had asked the ECJ to rule on whether the UK can pull out of the withdrawal procedure on its own.

Alyn Smith, a Scottish nationalist member of the European Parliament, and one of those who raised the case, said the ruling "sends a clear message to UK MPs ahead of tomorrow's vote that there is a way out of this mess".

"If the UK chooses to change their minds on Brexit, then revoking Article 50 is an option and the European side should make every effort to welcome the UK back with open arms," Mr Smith said.

The ECJ ruling is in line with an opinion delivered last week by a Court legal adviser, which boosted the hopes of British Brexit opponents of the possibility the scheduled March 29 departure from the EU could be avoided.

EU leaders have long insisted they would welcome Britain changing its mind, but many EU officials and legal experts had believed the approval of either all or most of the other 27 members states would be needed to halt Brexit altogether.

Some senior EU officials have said Britain should be allowed to remain but could be asked to give up some of the special terms it had acquired over the past four decades, notably a hefty rebate on its payments to the bloc's budget.

Theresa May delayed a parliamentary vote on her Brexit deal, conceding she would have lost. ( AP: Alastair Grant )

A second Brexit vote?

Mrs May's Environment Minister, Michael Gove, who campaigned for Brexit, dismissed the ruling by repeating the Government's insistence it would not reverse its decision to leave.

"We don't want to stay in the EU," Mr Gove told BBC radio.

"17.4 million people sent a clear message that we wanted to leave the European Union and that also means leaving the jurisdiction of the European Court of Justice.

"So this case is all very well but it doesn't alter either the referendum vote or the clear intention of the government to leave on March 29."

Arriving to meet EU counterparts in Brussels, British Foreign Secretary Jeremy Hunt called the ruling "irrelevant".

The majority of British voters would be "shocked and very angry" if Brexit were halted, he said.

Three of the four living former British prime ministers, John Major, Tony Blair and Gordon Brown, said a second referendum was the way to resolve the crisis.

But it is far from clear whether or how Britain could organise a new referendum, given the short time left until Brexit.

Many warn, however, that it could stir unrest. Opinion polls suggest any new majority for staying in the EU is narrow.

AP/Reuters