Brexit Party leader Nigel Farage on Tuesday urged Prime Minister Boris Johnson to lead Britain out of the EU without a divorce deal, threatening to fight his party "in every seat" otherwise.
"Given where we are, no deal is the best deal," Farage told more than 500 prospective parliamentary candidates from his recently-formed party, which topped the European elections in May.
"If, Mr Johnson, you insist on the Withdrawal Agreement, we will fight you for every single seat" in the next general election, he said.
Farage, a leading force behind the Brexit vote in 2016, warned Johnson against attempting to strike an agreement with Brussels, urging him to pursue a "clean break Brexit" instead.
Farage said the Brexit Party was prepared make way and strike a "non-aggression pact" with Johnson's governing Conservatives in any general election if the prime minister went for no-deal.
However, he said the Conservatives faced electoral annihilation otherwise.
"The only way they could win a general election is with our support," said Farage, who has been an MEP since 1999 but has failed seven times to get elected to the British parliament in elections going back to 1994.
"We could be their worst enemy or their best friend."
British politicians are still deeply divided over how or even whether to leave the European Union and the impasse has led to growing speculation that a general election may be imminent.
Johnson was due to speak to European Commission president Jean-Claude Juncker by phone later on Tuesday, while the government's chief Brexit adviser David Frost will head to Brussels for talks on a possible deal on Wednesday.
- 'Urgency to act' -
With the clock ticking, Labour leader Jeremy Corbyn met five pro-EU opposition leaders to thrash out a plan to stop a no-deal Brexit, following leaked official planning documents that this could lead to food, fuel and medicine shortages.
They "held a productive and detailed meeting on stopping a disastrous no-deal exit from the EU", the six opposition party leaders said in a joint statement.
"The attendees agreed on the urgency to act together to find practical ways to prevent no-deal, including the possibility of passing legislation and a vote of no confidence."
They committed to hold further meetings.
The pound rose sharply against the dollar and the euro -- by around 0.5 -- following the announcement.
Corbyn has said he plans to call a no-confidence vote in Johnson's government next week and if he wins it would be ready to lead a caretaker government.
But other opposition MPs favour passing a law that would force the government to ask the EU to delay Brexit.
Speaking to BBC radio after the meeting, Liberal Democrat leader Jo Swinson said they did not discuss who might lead a caretaker government if Johnson lost a confidence motion.
She has insisted it cannot be Corbyn due to his years of ambiguity on Brexit.
Ahead of the talks, Corbyn wrote in The Independent that Johnson was "cosying up" to US President Donald Trump in the hope of securing a free trade deal after Brexit.
"A No Deal Brexit is really a Trump Deal Brexit," he said.
- Suspending parliament 'unlawful' -
Britain's parliament is due to return on September 3.
But anti-Brexit politicians have been discussing plans ever since Johnson came to power last month vowing to take Britain out of the EU on October 31 with or without a divorce deal with Brussels.
Johnson has said he is hoping for a deal with EU leaders, describing the chances as "marginally" higher following G7 talks over the weekend.
But Johnson has not ruled out suspending parliament in order to allow a no-deal Brexit if he fails to come to an agreement with the EU in the next weeks.
Labour's Brexit spokesman Keir Starmer has said suspending parliament -- known as "proroguing" -- would be "unlawful" and "completely unacceptable".
Britain voted to leave the EU in a 2016 referendum but has already been forced to delay its exit twice after parliament opposed a deal struck between Brussels and Johnson's predecessor Theresa May.
Johnson wants Brussels to remove the withdrawal agreement's fallback provisions for the border with EU member Ireland.