Liberal Democrat leader Jo Swinson warned in her party conference speech on Tuesday that a no-deal Brexit would be like "burning your house down" as she pledged to cancel Britain's departure from the EU altogether.
The pro-EU Lib Dems have capitalised on the squabbles within the two main parties over Brexit, seeing their polling numbers soar after pitching themselves as the party to overturn the result of the 2016 referendum.
"The first task is clear. We must stop Brexit," said Swinson during her maiden conference speech as party leader.
"We are crystal clear: a Liberal Democrat majority government will revoke Article 50 on day one," she added, referring to the legal mechanism that has set in motion Britain's departure from the European Union.
"There is no Brexit that will be good for our country."
The party came second in the recent European parliamentary elections, leapfrogging both the governing Conservatives and opposition Labour Party.
Its unequivocal support for the EU was demonstrated when prominent MEP Guy Verhofstadt, who has been heading up the European parliament's efforts on Brexit, was invited to give a conference speech earlier in the week.
The Lib Dems have wooed MPs who support EU membership from both main parties, Conservative and Labour, and is set to perform well in a general election which many believe is imminent.
Labour has now called for a second referendum, but the Lib Dems are the only party promising to immediately overturn the result of the Brexit referendum and keep Britain in the European bloc.
Prime Minister Boris Johnson has promised to take Britain out of the EU, with or without a deal, on October 31.
"The next few weeks are about deciding the kind of country we are and who we want to be," Swinson told the party faithful in the south coast resort town of Bournemouth.
"The truth is, you can't plan for no-deal.
"Planning for no-deal is like planning to burn your house down. You might have insurance, but you're still going to lose all your stuff."
She also said her party would be the ones to "defeat nationalism and populism".
"For so many, the 2016 referendum ushered in a new kind of politics. Driven by hate, fear and division," she said.
"We can change our politics, stop Brexit and win a brighter future."