Boris Johnson could be forced to request Article 50 extension and delay Brexit within days as opposition parties join forces

Discussions under way on plan to bring forward deadline for extension from current date of 19 October

Boris Johnson could be forced to request a delay to Brexit as early as next week, after opposition parties began discussions on a new plan to block a no-deal departure from the EU.

The prime minister has vowed to take the UK out of the EU on 31 October with or without a deal.

But the so-called Benn Act, pushed through parliament by the ‘rebel alliance’ earlier this month, requires him to seek an extension to the Article 50 negotiation process by 19 October unless he manages to secure parliamentary support by that date for a withdrawal agreement or a no-deal outcome.

Liberal Democrat sources confirmed that they are now working with other opposition parties to bring the deadline forward, though agreement has not yet been reached on a new date.

Although the change would require fresh legislation, it is understood that this could be forced thro​ugh a parliament where the Conservatives no longer have a majority in time to force Mr Johnson to go to Brussels as early as next week.

Lib Dem leader Jo Swinson said: “We simply cannot afford to wait until 19 October to see whether or not the Prime Minister will refuse to obey the law again.

“Liberal Democrats will be working with and talking with people across the different parties to find a way to remove that threat of a no deal Brexit more quickly. It is vital that we do this for our country’s future.”

A change to the Brexit extension deadline could bring forward the date of the expected general election, as Labour has made clear it will table a vote of no confidence in Mr Johnson as soon as no-deal has been definitively ruled out.

The precise means for forcing an earlier date has not yet been determined, but Ms Swinson said her party would be considering “all options”.

Lib Dem sources confirmed that talks were taking place with cross-party opponents of a no-deal Brexit across the Commons, who would have to unite behind any initiative to drive it through parliament.

Jo Swinson (REUTERS)

The development came as Lib Dem deputy leader Sir Ed Davey warned that the Benn Act’s provisions to block no-deal may not be “watertight”.

Sir Ed told BBC Radio 4’s Today programme: "The key thing of course is implementing the extension of article 50 so that we can get no-deal totally off the table.

“It might need an extra law, who knows? The key thing is the implementation of the extension of article 50.”

Asked if the bill was watertight, Sir Ed said: “I’ve certainly seen the opinion of a number of very notable lawyers, that it’s not watertight – and if that’s the case we may need another bill to ensure that no-deal Brexit is completely taken off the table.

"But even with another bill, we have to force the prime minister to extend article 50 to get to this implementation, as well as the law."