The Liberal Democrats have accused other anti-Brexit parties of damaging the chances of success in the European elections by refusing to fight on a joint ticket.

Vince Cable lashed out at The Independent Group and the Greens for rejecting his pleas to stand joint candidates on 23 May, to boost the number of MEPs demanding a second referendum.

The Lib Dem leader revealed that his party proposed fighting together – a move that one election expert has predicted could have delivered an extra six seats in Brussels.

Frustrated campaigners for a Final Say public vote also believe a unified campaign would have excited voters and delivered an even greater reward.

Sir Vince said voters would be forced to choose between “a variety of different parties offering the same message”, under a proportional voting system.

“It would be better, I think, from the point of view of the supporters of British membership of the EU if we were fighting together under the same banner,” he told BBC Radio 4.

Farage launches his new Brexit Party: in pictures Show all 10 1 /10 Farage launches his new Brexit Party: in pictures Farage launches his new Brexit Party: in pictures Nigel Farage speaks at the launch of his new Brexit Party's campaign for the European elections Reuters Farage launches his new Brexit Party: in pictures Brexit Party candidate Annunziata Rees-Mogg, sister of Conservative MP Jacob Rees-Mogg, speaks at the launch AFP/Getty Farage launches his new Brexit Party: in pictures A supporter waits for Farage to speak AFP/Getty Farage launches his new Brexit Party: in pictures Supporters wait for Farage to speak AFP/Getty Farage launches his new Brexit Party: in pictures Farage's socks Reuters Farage launches his new Brexit Party: in pictures Farage and prospective candidate Annunziata Rees-Mogg wait at the launch AFP/Getty Farage launches his new Brexit Party: in pictures Supporters listen as Farage speaks AFP/Getty Farage launches his new Brexit Party: in pictures Free T-shirts for all attendees AFP/Getty Farage launches his new Brexit Party: in pictures Posters on the seats for supporters of the Brexit Party AFP/Getty Farage launches his new Brexit Party: in pictures A safety sign is pictured AFP/Getty

“Certainly that's something we would like to have seen, but that wasn't possible, we didn't get a positive reaction to that, so we are going on our own.”

Sir Vince added: “People out there who've seen this argument polarised would probably have preferred us to fight under the same banner and certainly that's something we would have wanted.”

It is understood that the deadline for registering with the Electoral Commission as a joint entity for the European parliament elections passed two weeks ago.

Change UK, the new party name for The Independent Group, has said it wants “no alliance and no pacts, but to be a new party standing on its own”, a stance echoed by the Green party.

The Independent revealed today that experts believe Theresa May has already run out of time to stop UK participation in the elections, because her deal cannot be fully ratified by 22 May.

And Donald Tusk, the European Council president, has suggested the UK will continue to be represented in the assembly for “several months – maybe longer”, as Tory-Labour compromise talks remain deadlocked.

The Lib Dems have now announced their full list of candidates, campaigning for a fresh Brexit referendum and to Remain in the EU.

Of the 73 UK seats in the European parliament, the Greens currently have three and the Lib Dems just one, after elections five years ago.

Under the PR system, a party needs to reach a minimum threshold to win a seat, which varies by region from 10 per cent in the south-east to 30 per cent in the north-east.

The Commission has now approved the application by the breakaway group of former Labour and Tory MPs to become Change UK in time for the poll.

However, candidates will have a blank space next to their names on the ballot papers after a proposed logo was rejected.