Lib Dem leader Sir Vince Cable urges Change UK to ditch "petty tribalism" and form an electoral alliance.

Cable has failed to persuade the new anti-Brexit party of former Conservative and Labour MPs to form a pro-Remain alliance for the upcoming European elections and beyond.

Supporters fear this refusal to cooperate will split the Remain vote and hurt anti-Brexit parties.

Cable told Business Insider that an electoral alliance was "common sense" and that millions of Remain voters would feel "angry and betrayed" if parties did not work together.

Lib Dem Tom Brake hit back at Change UK suggestions that Lib Dem members should quit the party and join Change UK.

LONDON — The Liberal Democrats have accused a fellow anti-Brexit party of "petty tribalism" after Change UK questioned the future of the Lib Dems and told its members and donors to quit and join their party instead.

Change UK, the pro-Remain party set up in February by eleven former Conservative and Labour MPs, is being urged by some of its backers to form an electoral alliance with the anti-Brexit Lib Dems.

Supporters of this idea argue that it would maximise the Remain vote and prevent it being split across a number of parties. Lib Dem leader Sir Vince Cable backs it and wanted it to take shape before the European elections next month.

However, Change UK opposes an electoral alliance, and aims to take members, donors, and voters from the Lib Dems.

Its economic spokesperson, Chris Leslie MP, told Business Insider last week that the Lib Dems had "fallen below a critical mass" and had "baggage," and has previously said that they have an "issue of trust" with the public.

Speaking at the Lib Dems' European elections launch on Friday, Cable said it was a "pity" that Change UK did not want to form an alliance, and accused the new party of betraying millions of Remain voters nationwide.

He told Business Insider that the Lib Dems would "rise above it" and said: "There are millions of people out there willing us to work together and they will feel angry and betrayed if they find petty tribalism is trumping that.

"That's the old politics — and I thought they [Change UK] were trying to get away from it. We certainly are.

"At the end of this, common sense will prevail."

He added: "There are individual comments by individual members but that isn't my sense of where they collectively are, to the extent which they have a collective voice."

Lib Dems have more 'strength and depth' than Change UK

Cable was supported by the Lib Dem Brexit spokesperson, Tom Brake, who told Business Insider that his party was the one "with the strength and depth" to be successful in next month's European elections.

"We will have a manifesto. We haven't had any difficulties with our candidates," Brake said. Two Change UK members this week stood down as European election candidates for racist and sexist remarks posted online.

He added: "They [Change UK] will be able to look at the last real electoral test before the European elections, which is the council elections where we expect to do very well, in contrast to Change UK, which hasn't got any candidates standing because they weren't actually formed as a party at the point when the nominations were opened."

Cable used the party's European elections launch to describe the Lib Dems as "the party of Remain" and said that a vote for his party late next month was a vote to stop the United Kingdom's exit from the European Union.

Got a tip? Email this reporter at apayne@businessinsider.com or Twitter DM at @adampayne26.