But the rival campaigns show up fractures in the anti-Brexit movement that make neither scheme likely to succeed.

Johnson has promised to push through Brexit by October 31, with or without a deal, setting the scene for a showdown in parliament where a majority of lawmakers are opposed to an EU divorce without a transition agreement.

With parliament the main obstacle to Johnson's "do or die" pledge, lawmakers are urgently seeking a way to remove him or change the law to delay Brexit.

Jeremy Corbyn, the veteran socialist leader of the Labour Party, said lawmakers should support a vote of no confidence and back him to lead a "strictly time-limited temporary government" that would postpone Brexit and hold an election.

"This government has no mandate for No Deal, and the 2016 EU referendum provided no mandate for No Deal," Corbyn said.

"I therefore intend to table a vote of no confidence at the earliest opportunity when we can be confident of success."

A handful of lawmakers from Johnson's own Conservative Party said they would listen to Corbyn's proposals.

However, his chances of success were crippled by the leader of the anti-Brexit Liberal Democrat party, Jo Swinson, who said Corbyn was not the right figurehead for an emergency government.

"We are facing a national crisis. We may need an emergency government to resolve it but if Jeremy Corbyn truly wants that to succeed, surely even he can see, he cannot lead it," she said.

Swinson's rival idea for a senior parliamentarian to lead a national unity government is unlikely to be accepted by Corbyn.

Britain's electoral law lets another party try to form government within 14 days of a successful no-confidence vote, but only if they have a majority in the 650-seat parliament.

Johnson has a working majority in parliament of just one seat, including several lawmakers who have said they could vote to bring down the government.

However, without the Liberal Democrats' 14 votes, Corbyn's plan is unlikely to succeed. And without the support of Corbyn and his sizeable circle of committed supporters, any other plan also has little chance.

A spokeswoman for Johnson's office said the Labour leader was showing contempt for the 2016 referendum.

"Jeremy Corbyn believes that the people are the servants and politicians can cancel public votes they don't like," she said.

Lawmakers return from their summer break on September 3 for a battle over Brexit that will determine the fortunes of the world's fifth-largest economy.

Labour's business spokeswoman said a challenge in parliament could come days later.

Opponents of a sudden departure without a deal say it would be a disaster for what was one of the West's most stable democracies, shattering supply chains, damaging global growth, and weakening Britain's standing in the world.

Brexit supporters say while there may be short-term disruption, it would provide a clean break from the struggling bloc and eventually allow the economy to thrive.

Corbyn is a divisive figure and even his own party would struggle to form a majority of his own.

Australian Associated Press