Vince Cable has staked the Liberal Democrats’ claim to be the leading remain party in the European elections, as he unveiled a forthright new slogan for the campaign: “Bollocks to Brexit.”

The phrase, previously plastered on stickers and T-shirts by ardent remain supporters, is now emblazoned across the Lib Dem manifesto for the 23 May poll – though more squeamish candidates will have the option of one that just says “Stop Brexit”.

Buoyed by strong results in last week’s local council elections, and unencumbered by the nuance of Labour’s position, Cable insisted the Lib Dems were the best-equipped party to challenge the message of Nigel Farage at the poll later this month.

“We are clearly the best organised, we have been leading the People’s Vote argument for three years and we’ve been the pro-Europe party for 50 years. We are credible and people recognise our unwavering clarity and commitment.

“We are taking it very seriously, we have a high-pressure social media campaign where we are doing more than Farage’s people,” he said, adding, “we are out of the traps early, and expect to do well. But it is a very unpredictable scenario.”

Cable said he regretted the fact that the Lib Dems were not able to fight a “common campaign” with Change UK, the new party formed of breakaway Labour and Tory MPs.

He said he expected the Lib Dems to beat the party in the elections, though stressed he would not expending energy attacking any other remain party. “I would be very surprised if they made a big breakthrough, but they might,” he said.

Asked why an alliance had been impossible, he said it had come down to both haste and lack of will. “I don’t think they disguised the fact they wanted to stand on their own – and it was very clear there was not the will to make things happen.”

Q&A How do European parliamentary elections work in the UK? Show Hide The UK elects 73 members (MEPs) to the European parliament, which is made up of 751 MEPs elected by the 28 member states of the EU. The UK is split into 12 European electoral regions, and each region is represented by between three and 10 MEPs. The constituencies are:

South East England (10 MEPs)

London (8)

North West England (8)

East of England (7)

West Midlands (7)

South West England (including Gibraltar) (6)

Yorkshire and the Humber (6)

Scotland (6)

East Midlands (5)

Wales (4)

North East England (3)

Northern Ireland (3) You can find out who is standing for election in your area here. In England, Scotland and Wales, voters can choose to vote for one party or individual. The ballot paper lists the parties standing with the names of their potential MEPs, as well as any individuals who are standing as independent candidates. The D’Hondt method of proportional representation is used to calculate how many seats each party or individual receives. In Northern Ireland, the single transferable vote method is used, where each voter ranks candidates in order of preference, marking 1 beside their most preferred candidate, 2 beside their second choice, and so on. These votes are then used to allocate Northern Ireland’s three MEPs. Those elected as MEPs on 23 May will represent the UK when the new European parliament assembles on 1 July, until such time as the UK ceases to be a member of the European Union.

Cable confirmed that the Lib Dems are now in talks with Change UK about fielding a joint candidate at the Peterborough byelection, which is taking place on 6 June. “There are conversations and I’m encouraging that.”

Rather than one of the parties selecting a candidate and the other stepping aside, he said the pact was likely to involve an independent, standing with the backing of the respective parties.

Cable confirmed that he plans to step aside after fighting the European election campaign, in time for a new leader to be in place by the summer.

He declines to set a firmer date. “I will see this through, and it’s up to the party organisation to get a timetable in place for selecting a new leader between now and the summer,” he said.

Facebook Twitter Pinterest Chuka Umunna of Change UK – the Independent Group. The Lib Dems hope to join forces with the party to fight the Peterborough byelection. Photograph: Nils Jorgensen/REX/Shutterstock

“But it’s all very orderly and consensual, which is what I wanted to happen. You get leaders who are pushed out, fall under trains and whatever. I just wanted it to be an orderly succession.”

He has faced criticism for failing to make the media impact of his predecessor, or improve the Lib Dems’ poll ratings. But he hailed last week’s strong local election results as evidence that a steady approach of rebuilding the party from the bottom up is finally paying dividends.

“Infrastructure and organisation really does matter,” he said. “The lesson for other parties is you can’t function without that. There is no future sitting in London sending out messages.”

He said no new party – or party leader – could hope to exactly replicate the success of En Marche and Emmanuel Macron, the French leader to whom Change UK’s Chuka Umunna is sometimes compared.

“One thing I would point out, in I hope not too an unfriendly way, is that this is not France. Even if Macron were a success story – and those people in yellow vests may say otherwise – it has happened because of their presidential system,” he said. “It can’t happen here, you have to do something totally different in the UK.”

Cable inherited the Lib Dem leadership after a underwhelming performance at the 2017 election under Tim Farron, who found his campaign dominated by an embarrassing row over whether he believed gay sex was a sin.

Cable says he now believes that if another general election is held in the next 12 months, as many in Westminster believe is increasingly likely, his party is poised to make significant gains.

“One of the things I’ve been doing in the background is building up the number of marginal seats. We were 64 at one point, but we thought that if we could get from 12 to 20 – or potentially 30 – that was our range,” he says. “I think a whole lot more seats have now become feasible again.”

Cable has devoted some of his time recently to writing a booklet called Beyond Brexit, tackling issues such as the dominance of the big tech firms, and rising inequality.

He acknowledges he would much rather have spent his spell as Lib Dem leader working on those issues, instead of fighting to stop Brexit.

“It has just become mind-numbingly … boring isn’t the right word but perhaps repetitious. The same slogans, no new arguments and very unproductive. That’s why people are getting angry, they know the arguments, they’ve heard them, they aren’t going anywhere. It’s pent-up anger on both sides.”

He expresses concern about the rise of populism against that backdrop; and says part of his argument in the European election campaign will be that Lib Dem MEPs will join the growing Alliance for Liberals and Democrats for Europe group (ALDE), along with Macron’s En Marche party, and the Spanish Ciudadanos.

“This is now the dominant force, fighting the populists, and we’re part of that movement and it will have a significant influence,” he says. “It’s a common European front for liberal values, against the extremists and the populist fringe, and as British MEPs they wouldn’t be on their own – they would be part of the big battalions.”