When Chuka Umunna and his six Labour colleagues dramatically resigned from their party in early February, Umunna said he intended to move quickly and form a new party by the end of the year. But like so many ideas that have been formed around the Brexit process, that plan had to change even faster than intended.

When Theresa May conceded that an extension to the Brexit process would require British participation in European elections, Umunna and his fellow MPs found themselves needing to set up a new party, Change UK, in just two days.

Just a few days from the vote, the optimism of that moment has been tempered by the hard reality of the polling numbers, with the party currently at about 4%. But Umunna reflects on the urgency with which the nascent party swung into action.

“We literally registered the day after the Electoral Commission said to us: ‘You would need to do this urgently.’ And we said: ‘What does that mean?’ And they said: ‘Like, now,’” he remembers, sitting in the sunshine on a brewery rooftop in Cardiff, before one of the rallies he is fronting in many of the remain-leaning towns and cities where Change UK hopes to win support.

The party, whose campaign centres on forcing a new referendum and remaining in the EU, had to come up with a name, a brand and a campaign within hours. “It’s a startup. You have no idea what is going to happen at all,” he says.

“When you leave one of the established parties, you are putting everything on the line. You don’t do this in expectation of loads of glory, becoming the prime minister. You do it for what you believe. The one thing that people come up and say to you is to tell you that you are really brave. It’s everywhere I’ve gone, in every part of the country.”

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As startups go, though, this one has had its teething problems, and the scramble to launch has led to a campaign that has felt somewhat haphazard. Their original name, the Independent Group, was refused by the Electoral Commission, as was their logo design for including a hashtag. Their new name sparked a row with petitions site Change.org, who accused them of using their brand.

Meanwhile, Umunna and his colleagues have had to contend with a series of dismal polls which has also shown strong results for the resurgent Liberal Democrats. The defection of a candidate to the Lib Dems has not helped matters.

Facebook Twitter Pinterest Chuka Umunna and Heidi Allen at a European elections rally in Cardiff. Photograph: Dimitris Legakis/Athena Pictures

Change UK’s leader, Heidi Allen, who insisted there was no prospect of her moving on by saying “it wouldn’t look good if I defected from one party and defected to another a few weeks later,” said the group accepted that this campaign would be imperfect. “At the end of the day, what is more value to the country? Us trying, or just sitting by and letting it go to the wall as it is, if we leave it in the hands of the Tories and Labour?” she said.

But on Monday she did seem to acknowledge that the party in its current form might be short-lived. “Will I stand again in South Cambridgeshire, my constituency, as Change UK?” she said. “Whatever format, let’s hope we know … if we’ve managed to bring together other MPs from the House of Commons, the format might be slightly different.”

Ambiguity from the leader on the matter of the party’s future may be considered a PR headache. But communication has long been an issue for the understaffed group: several would-be activists or advisers who offered help in the early days of the Independent Group’s launch said there was no system for responding to them.

While Umunna’s speeches, as well as the tub-thumping oratory of his colleagues Mike Gapes and Anna Soubry, receive rapturous receptions at their rallies in Bath and Cardiff, some appearances by their candidates and MPs have verged on the comic.

MP Joan Ryan brought chuckles at the party’s Bath rally when she implored the audience to look at their palms and said, deadpan: “It’s there, the future is in your hands.”

Jessica Elgot (@jessicaelgot) A bus! It’s a real election now pic.twitter.com/xIfF284zzL

Even senior party sources concede that the wonky black-and-white branding, particularly of their battlebus, may be a mistake – one tweet observed: “I didn’t know you could print a Word document straight on to a bus” – and that stripes only made sense when the party’s nickname was “TIG-ers”. But the party insists that voters do not care about such trivial things.

Indeed, despite organisational dysfunction, Change UK has still racked up a mostly impressive candidates list: former MPs, television presenters and business owners, as well as tens of thousands of new registered supporters.

Having left well-oiled party machines, Umunna and his colleagues found themselves doing the vast bulk of the work. Soubry said she believed she had personally read more than 1,000 of the 3,700 applications to be MEP candidates that the party had received. That process was far from watertight – two candidates were forced to quit within hours of the launch because of racist remarks on social media.

Umunna admits the group had hoped to take time to develop during the summer and launch by the end of the year. The election date changed all that. “We felt sitting it out wasn’t an option. Politics is so volatile and changeable, it’s not going to wait for you,” he says.

The polls, as well as suggesting low overall support, suggest that the party has a problem with name recognition. The difficulty in finding it on Google may also be a concern. A recent poll for YouGov found under a third of voters knew Change UK’s position on Brexit – despite their clear pro-referendum campaigning.

Facebook Twitter Pinterest Anna Soubry defected from the Conservative party to join the new group. Photograph: Dimitris Legakis/Athena Pictures

Umunna said he still did not believe that it was a political miscalculation to stand for election at this time – and insists there remains an appetite for something new in politics. “It’s the lowest vote shares for the two main parties in 100 years,” he says. “Our analysis that this is a moment for something new is absolutely accurate.”

The local elections threw up one major new challenge for Change UK – a reversal of fortunes for the Liberal Democrats. The party gained more than 1,000 council seats and are so far enjoying a buoyant EU election campaign, and fast appear to be the remainers’ party of choice in this election, at least in England.

In another harsh blow, Change UK’s lead candidate in Scotland, David Macdonald, then announced that pro-remain voters should now vote for the Lib Dems, which Umunna called “disappointing”. Some found irony in his additional observation that by changing party Macdonald had “let down his fellow candidates and activists”.

Change UK started out vowing no pacts with the Lib Dems, believing the brand was toxic from the coalition and its mixed fortunes under Tim Farron. Yet now, some senior Change UK sources talk about “realignment in the centre ground” – specifically with regards to the Lib Dems – in warmer tones than a week previously.

“Look, good luck to the Lib Dems,” Umunna says. “We want remain parties to do well. When we spoke to them after the local elections, we said: ‘Massive congratulations, well done, guys.’ The old Westminster way is to do down the Lib Dems. But we did mean it when we said country first.”

Umunna says that the main aim is now to add to the remain-voting total in the final tally of votes after the EU elections. “What we do is add to the remain vote – we don’t detract from it,” he says. “In my own constituency, for a lot of Labour voters to vote for a party of coalition, of austerity, it’s still a step too far. But we won’t plaster it all over our leaflets to attack the Lib Dems.”

One aspect of the criticism of Change UK, which has clearly riled Umunna, is the accusation that his party has not been collegiate with other remain parties like the Lib Dems and the Greens.

Facebook Twitter Pinterest Anna Soubry and Heidi Allen on the campaign trail. Photograph: Dimitris Legakis/Athena Pictures

“I think the commentary on this has been actually very unfair,” he says. “Since we’ve formed as a group we have engaged in unprecedented level of collaboration with other parties. I challenge anyone to find a greater champion of non-tribalism.”

He was particularly irritated by a row over plans to find a joint candidate for the Peterborough byelection with other remain parties, scuppered at the last minute after the candidate’s jitters about what he would do to the Labour vote.

That objection has led Change UK into a bitter argument with the People’s Vote campaign. Umunna helped to found that movement with his colleague Anna Soubry – a former Tory – but he now accuses several staffers, including ex-Labour spinners, of giving Labour too easy a ride over its support for a second referendum.

“Supposedly independent non-partisan staff of an independent non-partisan campaign – the People’s Vote campaign – were doing the Labour party’s bidding to stop there being a remain candidate in Peterborough,” he says. “That is the outrage.”

Umunna says the party will continue to grow and develop – even if this campaign sees no new Change UK MEPs elected. “This is about the national interest,” he says.

“We have always looked at the challenge in front of us and said: ‘What is the right thing to do by the country?’ I think after these elections the question is the same, and the answer is: the national interest first.”