A pro-Brexit protester waves a Union flag as he stands with "We Voted Leave" placards outside the Houses of Parliament in London on September 9. British Prime Minister Boris Johnson met his Irish counterpart in Dublin on September 9 as he battles to salvage his no-deal Brexit strategy and force an early election in the face of fierce opposition in Westminster. Photo: AFP

A damning UK Supreme Court ruling against British Prime Minister Boris Johnson this week has rekindled discussion within the European Union about another delay to Brexit, with the bloc drawing a line in the sand of mid-2020 at the latest.

The British parliament resumed on Wednesday after the court ruled that the chamber had been unlawfully suspended by Johnson, who insists he will take Britain out of the EU on October 31 - with or without a deal to manage the fallout.

But British lawmakers reject the most damaging, no-deal Brexit and, back at work, will now have more chance to upset Johnson's plans.

With the divorce deal stalled, the EU is expecting another delay to Britain's departure date after it was already postponed twice from the original March deadline.

"We are in favor of an extension if we also see what is the way forward, will there be a general election, a second referendum, will there be a Withdrawal Agreement," said Guy Verhofstadt, an EU lawmaker dealing with Brexit.

"I think that there is unanimity...to say 'OK, let's go forward with an extension if there is a clear path to a solution and unwinding of the situation we have today,'" he told EU lawmakers on Wednesday afternoon.

With a national election expected in Britain by the end of the year, the bloc currently sees that as the most likely justification of anther lag - a decision that would require the unanimity of the 27 states staying on.

The problem is, however, that Britain would need to request such an extension, which Johnson vows never to do and EU Brexit watchers speculate about him possibly stepping aside to let someone else make the step.

Under the law, the EU could also formally demand a delay - which Britain would need to agree to for it to take effect.

But diplomats and officials dealing with Brexit in the bloc's hub Brussels ruled out such a possibility, saying it would risk feeding Johnson's rhetoric about distant elites trying to frustrate the will of the people.

With many question marks over the fate of Brexit lingering three years since Britons voted out, EU leaders meeting in Brussels on October 17-18 will discuss the desirable length of any such delay.

The British prime minister will not be allowed in the room.

The House of Commons has passed a law demanding that London seeks a postponement until the end of January 2020 to avoid an abrupt split on October 31 should no new divorce deal be reached at the EU summit in three weeks time.

"January may be a bit too soon for us," said one EU diplomat. "It is far from clear that Britain would be able to sort itself out by then and we would risk another summit at the turn of the year to push back another no-deal prospect."