Pro-EU parties, including the Liberal Democrats, the Greens and the Independent Group, will not form pacts or alliances at the forthcoming EU elections, hoping to use the poll as a “soft referendum” to show a surge in support for remain.

If no Brexit deal is passed by parliament, the UK will be required to hold the poll on 23 May. The Lib Dems, the mainstream party hoping to capitalise most on anti-Brexit discontent, has almost finalised its manifesto and plans a huge operation of ground campaigning targeting remain voters.

“We want to use the momentum from the locals, which very few other parties will have, as a springboard for European elections,” a party source said. “Voters across all of Great Britain want to vote for a pro-remain party. We’re going to give them all the chance to vote Lib Dem.”

The TIG MP Chuka Umunna claimed his new party – Change UK – would be “the leading option on the ballot paper” arguing for a second referendum.

The breakaway group of former Labour and Tory MPs has invited its network of supporters to apply to be MEP candidates “to give the British people a real choice”.

The timeframe for potential candidates will require final applications to be submitted by Monday morning and interviews later next week. In its email to supporters, the group said it was expecting a high number of applications and potential candidates should be prepared for a significant commitment.

The party intends to carry out “background verification checks” on candidates, who must provide all their social media handles, in the hope of avoiding the embarrassments that have plagued many start-up parties.

Candidates will also be asked to “outline your perspective on why politics is broken and how it needs to change”, as well as setting out their commitments to the Nolan principles of public life – selflessness, integrity, objectivity, accountability, openness, honesty and leadership.

The group’s interim leader, Heidi Allen, a former Tory MP, said they would encourage “anyone who wants to see a people’s vote on Brexit, who wants to remain a full member of the European Union, and who wants to shake up and change our broken politics”.

The Green party is also hoping to capitalise on running with an explicitly pro-remain stance. Party co-leader Siân Berry said the Greens would “mobilise one of the strongest pro-EU movements anywhere” and would stress the importance of the elections to send a message.

“We will not let the government downplay how important these elections are. This isn’t just about the European Union – it’s about the country we live in,” she said.

“One thing we can agree on is that our politics is broken, and has failed to fix the intolerable inequality and insecurity which caused the Brexit vote. A vote for the Greens is a vote against this chaos, a vote for change, a vote to remain and a vote for an open and confident Britain.”

Renew, another emerging new party that has fought local elections, will also run pro-EU candidates in the EU elections. The party leader, Annabel Mullin, said the elections would be “seen by many as a soft referendum on EU membership”.

The two major parties are also likely to see applicants hoping to run on a remain platform. Stanley Johnson, the father of Boris Johnson and a former Tory MEP, has announced his wish to stand again for the party to make a pro-European case.