British lawmakers on Tuesday began a bid to stop Boris Johnson pursuing what they cast as a calamitous 'no-deal' Brexit, a challenge that a senior government source said would prompt the Prime Minister to press for a snap election on October 14.

More than three years after the United Kingdom voted to leave the European Union in a referendum, the outcome of the Brexit crisis remains uncertain, with a range of options from a turbulent no-deal exit to abandoning the entire endeavour.

Johnson implicitly warned lawmakers on Monday that he would seek an election if they tied his hands in talks to negotiate a last-minute divorce deal, ruling out ever countenancing a further delay to Brexit, scheduled for October 31.

That sets up an historic showdown between the Prime Minister and Parliament in a country once touted as a confident pillar of Western economic and political stability.

The sterling flirted with some of its lowest levels since 1985.

An alliance of opposition lawmakers and rebels in Johnson's Conservative Party put forward a motion on parliament's first day back from its summer break to launch their attempt to block a 'no-deal' exit. They are confident of victory.

Johnson cast the challenge as an attempt to force Britain to surrender to the EU just as he hopes to secure concessions on the terms of the divorce -- a step he said he would never accept. “It means running up the white flag,” Johnson told Parliament. “It would enable our friends in Brussels to dictate the terms of the negotiation.”

Just as Johnson began speaking, he lost his working majority in Parliament when one of his own Conservative lawmakers, Phillip Lee, crossed the floor of the House of Commons to join the pro-EU Liberal Democrats.

'Ready to fight'

In the eye of the Brexit maelstrom, it was unclear if opposition parties would support any move to call an election, which requires the support of two-thirds of the 650-seat House of Commons.

“If an election is called, I am absolutely ready to fight it,” Labour Party leader Jeremy Corbyn said after a meeting with leaders of other opposition parties, while adding that his priority was to prevent a no-deal Brexit.

Also read: PM Johnson faces mounting legal, political, diplomatic challenges

The pound, which has gyrated to the twists and turns of Brexit since the 2016 referendum and is highly sensitive to the prospect of a 'no-deal' exit, fell as low as $1.1959. Barring a minutes-long “flash crash” in October 2016, sterling has not regularly traded at such low levels since 1985.

Fears of an abrupt 'no-deal' Brexit were rising elsewhere. The European Commission said such a scenario was a “very distinct possibility” and French Foreign Minister Jean-Yves Le Drian said it was the most likely scenario.

US Vice President Mike Pence used a visit to Ireland on Tuesday to urge the European Union to negotiate “in good faith” with Britain.

The 2016 Brexit referendum showed a United Kingdom divided about much more than the European Union, and has fuelled soul-searching about everything from secession and immigration to capitalism, empire and modern Britishness. It has also triggered civil war inside both of Britain's main political parties as dozens of lawmakers put what they see as the United Kingdom's fate above that of party loyalty.

As Johnson played Brexit chess with lawmakers, opponents cast his tactics as undemocratic, including an order to suspend parliament for more than a month beginning next week. That has been followed by his threat to kick rebels out of the ruling party - some of them former ministers who left the cabinet just weeks ago.

Snap election threat

“I think we will have the numbers,” said one of the rebels, Conservative former finance minister Philip Hammond. “Prime Minister Johnson has always intended that there will be an election.”

The rebel alliance planned to put forward an emergency motion for a vote on Tuesday allowing its members to seize control of the parliamentary agenda the following day to try to pass legislation that would force Johnson to seek a three-month delay to Britain's EU exit.

Also read: Collapse us if you can, British government dares Brexit opponents

Johnson raised the stakes, however, effectively turning it into a confidence vote by making clear that if the government were defeated, it would hold a vote on Wednesday to approve an early election, most likely to be held on October 14.

“The Prime Minister's mood is determined,” his spokesman said. “He wants to get on with delivering on the result of the referendum and the UK leaving the EU on October 31st, ideally with a deal.”

His spokesman cast the rebel bill as “a blueprint for legislative purgatory”.

Also read: What are the options before PM Boris Johnson?

While Johnson said he did not want a snap election, a senior government source said lawmakers should be aware that it would be a consequence of their decision to vote against the government on Tuesday. “I don't want an election. You don't want an election. Let's get on with the people's agenda,” Johnson said on Monday at a hastily organised appearance outside Number 10 Downing Street.

Rebels say the government really wants an election but is trying to blame lawmakers for triggering one.

The US investment bank JP Morgan said an election would make a no-deal Brexit more likely.