A cross-party alliance of British MPs has voted to take control of Parliament in a bid to prevent the United Kingdom from leaving the European Union without a deal at the end of October.

Key points: Rebel Conservatives and Opposition MPs plan to bring forward a bill forcing the PM to delay Brexit unless MPs back a new deal or vote for a no-deal exit

Rebel Conservatives and Opposition MPs plan to bring forward a bill forcing the PM to delay Brexit unless MPs back a new deal or vote for a no-deal exit Mr Johnson is now expected to call a snap general election on October 14

Mr Johnson is now expected to call a snap general election on October 14 If Labour won, it would hold another Brexit referendum and allow the option of remaining in the EU bloc

Rebel Conservative MPs joined forces with the Opposition — voting 328 to 301 — to seize Wednesday's parliamentary agenda and bring forward a bill that would force Prime Minister Boris Johnson to delay Brexit unless a new deal was backed by MPs, or they voted for a no-deal exit.

Boosting the numbers were 21 Conservative MPs who defied the party whip, despite the Prime Minister's threat to expel defectors from the party.

Among the 21 to be expelled is Sir Nicholas Soames, the grandson of Britain's World War II leader Winston Churchill.

Mr Johnson has consistently said the UK must leave the EU on October 31 — with or without a deal — and he has put forward a motion to call a snap election on October 14.

After the vote, Mr Johnson vowed to stop "another pointless delay to Brexit".

"I don't want an election, but if MPs vote tomorrow to stop negotiations and compel another pointless delay to Brexit, potentially for years, then that would be the only way to resolve this," he said.

"I can confirm that we are tonight tabling a motion under the Fixed Term Parliament Act."

Britain's Prime Minister Boris Johnson speaks in the House of Commons. ( Reuters: UK Parliament/Jessica Taylor )

An election would pit the avowed Brexiteer against Labour leader Jeremy Corbyn.

If elected in a snap poll, Jeremy Corbyn's Labour Party would hold another referendum on the options for a Brexit deal. ( Reuters: Andrew Yates )

Mr Corbyn has long demanded an election as the best way out of the crisis, but many of those seeking to prevent a no-deal Brexit say Mr Johnson could time the poll to ensure Parliament cannot prevent an October 31 departure with or without a deal.

Any attempt to go to the polls early requires a two-thirds majority.

Mr Corbyn told Mr Johnson he must allow the Brexit delay bill, to be discussed on Wednesday, to be dealt with before trying to call an election.

If elected in a snap poll, Labour would hold another referendum on the options for a Brexit deal.

Remaining in the bloc would be an option on the ballot paper.

If Mr Johnson's Conservatives reclaimed a majority in the House of Commons, Britain would leave Europe with or without a deal.

Mr Corbyn welcomed today's result, saying the priority was to delay Brexit, despite threats of a snap election.

"We live in a parliamentary democracy … we do not have a presidency but a Prime Minister. Prime Ministers govern with the consent of the House of Commons, representing the people in whom the sovereignty rests."

Johnson loses majority after defection

Earlier in the day Mr Johnson lost his working majority in the House of Commons after a Conservative MP sensationally defected to a rival party as the PM addressed the chamber.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 34 seconds 34 s Conservative MP Phillip Lee defects during Boris Johnson's speech

Shortly after crossing the floor, Phillip Lee — who supports a second EU referendum — released a strongly worded statement announcing he had joined the centre-left Liberal Democrats.

Dr Lee said Brexit divisions had "sadly transformed this once great party into something more akin to a narrow faction in which one's Conservatism is measured by how recklessly one wants to leave the European Union".

He also said the Conservative Government was "putting lives and livelihoods at risk unnecessarily and it is wantonly endangering the integrity of the UK".

"More widely, it is undermining our country's economy, democracy and role in the world," Dr Lee wrote.

"It is using political manipulation, bullying and lies. And it is doing these things in a deliberate and considered way."

ABC/wires