Video report by ITV News Political Correspondent Daniel Hewitt
Leaving the EU without a deal would be like "burning your house down", Liberal Democrat leader Jo Swinson has told her party conference.
After recently announcing her party would revoke Article 50 if it won a majority in a general election, the East Dunbartonshire MP closed the four-day event by reiterating her pledge to stop Brexit.
She received a standing ovation and sustained applause from party members as she took to the stage in Bournemouth, standing without a lectern.
She opened her speech by paying tribute to the party's "fabulous squad" of 16 MEPs, seven new MPs and 700 extra councillors, before launching a scathing anti-Brexit message.
Prime Minister Boris took a bruising in the speech - in which she attacked what she calls his pursuit of a no-deal Brexit.
Mr Johnson has vowed to take the UK out of the European Union by the October 31 deadline "do or die", deal or no deal.
But Ms Swinson told Lib Dem members on the Dorset coast that Mr Johnson's spending on no-deal preparations is "sickening".
"The truth is you can't plan for no deal. Planning for no deal is like planning to burn your house down," she said.
"You might have insurance, but you're still going to lose all your stuff."
She also hit out at his recent choice of insults, in which he called ex-PM David Cameron a "girly swot" and Jeremy Corbyn a "big girl's blouse".
She said: "If he thinks being a woman is somehow a weakness, he's about to find out, it is not."
And she criticised the prime minister's ability to negotiate a Brexit deal before the deadline, citing a skipped joint press conference as a failure.
She said: "He claims he could negotiate a Brexit deal in a month - I wouldn't hold out much hope, yesterday he failed to negotiate where to have a press conference.
She also told party members she was standing before them as their candidate for prime minister.
It comes a day after she defended to ITV News Politics Editor Robert Peston her plan to revoke Article 50 - effectively stopping the Brexit process.
She said it would not be undemocratic stop Brexit if the party won a general election, because people will understand "very clearly" what the Lib Dems stand for.
Voters at the conference voted overwhelmingly to back her policy, but Lib Dem MP Sir Norman Lamb was among a few to condemn it.
Another to criticise the move was Greens MP Caroline Lucas, who told ITV News podcast Acting Prime Minister that promising to revoke Article 50 is "arrogant" and "self-indulgent".
Speaking to ITV News Political Correspondent Paul Brand, the MP for Brighton and Pavillion said the pledge to effectively cancel Brexit is "dangerous" and "imperils democracy".
Ms Swinson also insisted to Peston that she is not the leader of a single issue party.
At the suggestion the party had morphed into the anti-Brexit Party - as opposed to Nigel Farage's Brexit Party - she said: "We are not a single issue party, we are a party with more than a century of liberal heritage.
"And we want to create an open, fair and inclusive society."
Ms Swinson predicts Brexit would "hurt" the country's economy - one of the core reasons the party this week agreed to adopt cancelling Britain's EU exit if it wins power at the next election.
Watch Robert Peston's video report on his interview with Lib Dem leader Jo Swinson
The former minister told the conference: "The first task is clear. We must stop Brexit.
"And we are crystal clear: a Liberal Democrat majority government will revoke Article 50 on day one because there is no Brexit that will be good for our country.
"Brexit will put lives at risk. Brexit will hurt our economy. This Brexiteer Government wants to pay for their ideology with other people's jobs."
Watch Jo Swinson's full speach to the Lib Dem conference here.