The Liberal Democrats’ annual conference is due to begin in Bournemouth, with the party’s leader hoping to convince members to back a new policy of scrapping Brexit without another referendum.
Jo Swinson says the UK got into a mess as a result of having a referendum.
And she believes revoking Article 50 – the formal process to leave the EU – is the only satisfactory way out.
The party is enjoying a resurgence on the back of its anti-Brexit stance.
Up until now, the party’s policy on Brexit has been to campaign for another referendum – in which it would again campaign for the UK to stay in the EU.
MPs in all parties are preparing for a Brexit-themed general election, and Ms Swinson wants her party to have the most unequivocally anti-Brexit message – that the Lib Dems would immediately scrap Brexit.
Parliament has so far denied Prime Minister Boris Johnson’s request for an autumn election, because opposition parties wanted to first make sure a bill designed to avoid a no-deal Brexit became law.
But since the bill, which seeks to force Mr Johnson to ask for a extension to the deadline, has been given Royal Assent, opposition MPs are preparing to start their general election campaigns.
Revoking Article 50 would effectively undo the legal mechanism under the EU’s Lisbon Treaty that was triggered to start Britain’s withdrawal from the European Union.
If Lib Dem members back their leader’s move, revoking Article 50 would be written into the party’s next election manifesto.
Lord John Kerr, the British diplomat who was involved in drafting Article 50, has publicly said the clause is reversible.
Ms Swinson is expected to take questions from conference delegates at the Bournemouth International Centre on Sunday, following a speech by her predecessor Sir Vince Cable.
It is likely to be Mr Cable’s last conference as a Lib Dem MP as he has said he will not contest his Twickenham seat at the next election.
Ms Swinson’s main speech will be held on Tuesday, the last day of the four-day conference, and will follow a tribute to the party’s former leader, Paddy Ashdown, who died in December.
And Chuka Umunna, the former Labour MP who joined the Lib Dems three months ago, will address party members on Monday in his role as Treasury and business spokesman.
The Lib Dems currently have 17 MPs, having been boosted by a victory in the Brecon and Radnorshire by-election and defections from both Labour and the Conservatives since the summer.