The Liberal Democrats launched their European election campaign on Friday in east London with a simple message, Stop Brexit, but expressed disappointment that there was not a single pro-Europe grouping.

The “unapologetically pro-European party” slate of 70 candidates includes local councillors, a chartered engineer, a former journalist, and those who are new to politics.

The party leader, Vince Cable, said it was a pity that Change UK, which launched its European election campaign last week as the anti-Brexit party, had ignored the Lib Dems’ offer to stand on a united slate. “We should be standing together,” he said. “The millions of people who want to remain would expect us to stand together.

“The Liberal Democrats made it clear we were happy to work with others but it wasn’t reciprocated.” He said the Lib Dems were the more established party and expected to benefit from anti-Brexit sentiment.

Speaking in Wapping, east London, Cable said his “exit from Brexit” catchphrase was first ridiculed but was now the mainstream and likened the party’s stance to its opposition to the 2003 invasion of Iraq. “At the time we were regarded as way out on a limb, unpatriotic – and we were vindicated, we were proved right. And that’s why I believe we will be right about Europe.”

Siobhan Benita, a former civil servant and the Lib Dems’ candidate for mayor of London in 2020, opened the campaign launch with a call to end the “national humiliation” of Brexit. “The whole Brexit fiasco has highlighted how dysfunctional the Conservative and Labour parties have become,” Benita said. “I knew then and I know now that our country is so much better than this. Whatever your politics, it’s safe to say the Conservatives and Labour have let everybody down.”

Benita said it was time for a new type of politics and described herself as the “original Tigger”, a nickname for Change UK supporters, because she had previously campaigned as an independent. She said she was drawn to the Lib Dems because of the party’s consistent campaign to stop Brexit.

Luisa Porritt, a communications director and former journalist, said she was standing as a candidate because “it’s a way for the electorate to signal to the government that they want a people’s vote”. She added: “I think going for the European parliament is another way of making sure a really strong liberal pro-European voice is heard in the parliament and counteract the Eurosceptism we saw in 2014.”

Porritt said it was a “concern” that other anti-Brexit parties had not come together on a united slate. “The Liberal Democrats extended the hands of friendship to Change UK and the Greens because we see this [Brexit] as an existential issue, but those parties didn’t want to meet with us.”

Rosina Robson, who works for a trade association, is standing for Yorkshire and the Humber. She said she was given amazing opportunities as a student because the UK was in the EU, “so why should the next generation be deprived of that”?

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She added: “Now is the time for all sorts of people, like me, who didn’t necessarily see themselves as a politician, to stand up for what they believe in.”

Rabina Khan, a local councillor who is standing in London, said she joined the Lib Dems eight months ago because “they are the only party who have consistently campaigned to remain in the EU and have been campaigning for the people’s vote. They are the consistent one.”

Catherine Bearder, who is standing in the south-east, did not believe the European election was a proxy for a second referendum. “It’s not a proxy referendum, it will be a temperature gauge,” she said.

She added: “The EU election is not about a protest, it’s about electing representatives. People need and deserve candidates who will work on their behalf … That is how we will be working.”