The Liberal Democrats will start the campaign to cancel Brexit entirely when the party meets for its autumn conference on Saturday.

The party faithful has descended upon Bournemouth’s seafront to get the conference season under way in what continues to be a fractious time in British politics.

As Prime Minister Boris Johnson looks to weather the storm following the ruling from Scottish judges this week that his advice to the Queen to suspend Parliament was unlawful, the Lib Dems are looking to capitalise and mobilise supporters in Dorset in preparation for a snap election.

A pro-EU demonstrator holds up a home-made poster protesting against prorogation outside the Court of Session in Edinburgh (Andrew Milligan/PA)

Parliament has so far denied Mr Johnson’s request for an autumn trip to the polls as opposition parties look to see the Benn Bill – legislation that demands the PM extend the Brexit deadline until January 2020 rather than take Britain out of the European Union without a deal – enshrined in law.

But with Royal Assent for the Bill now achieved and no majority in the House of Commons for the PM, both the Conservative Party and its rivals are gearing up for another Brexit-themed election.

Lib Dem leader Jo Swinson is looking to take her party into that election as the party most unequivocally in favour of staying in the EU.

She wants to sign her colleagues up to the policy of revoking Article 50 – a move that would cancel the divorce from Brussels without the need for a second referendum.

Labour’s policy would involve renegotiating a deal with Brussels and putting that to a confirmatory vote, should the party win the next general election.

Revoking Article 50 – effectively undoing the mechanism under the EU’s Lisbon Treaty that was triggered to start Britain’s withdrawal – would be written into the next Lib Dem election manifesto if members at the conference back the move.

Lord John Kerr, the veteran British diplomat who was involved in drafting Article 50, has publicly said the clause is reversible.

Mrs Swinson said: “We got into this mess as a result of having a referendum in the first place and that (revoking Article 50) is the only satisfactory way out of it.”

The party leader is due to take questions from conference attendees at the Bournemouth International Centre on Sunday, following a speech by her predecessor Sir Vince Cable.

Berger joins Liberal Democrats
Luciana Berger with Liberal Democrat leader Jo Swinson (right) after the former Labour MP announced she had joined the Lib Dems (Jonathan Brady/PA)

The East Dunbartonshire MP will close the four-day conference with a speech on Tuesday, with a tribute to former leader Paddy Ashdown, who died in December, due to take place beforehand.

Mrs Swinson has played an active part in convincing MPs to switch allegiance and join the Lib Dems, having seen former Tory minister Dr Philip Lee, ex-health committee chairwoman Dr Sarah Wollaston and former Labour and one-time The Independent Group (TIG) members Luciana Berger and Angela Smith defect in recent weeks.

Chuka Umunna, who joined the Lib Dems under Sir Vince’s leadership, will address party members on Monday in his role as Treasury and business spokesman.

Environment and climate change spokeswoman Vera Hobhouse MP will give her speech on Saturday morning before Baroness Brinton, the party president, closes proceedings in the afternoon.