A pro-European Union political party formed to shake up U.K. politics has split, four months after it was founded.

Change UK says it now has five lawmakers, down from 11. The six departures include the party's leader, Heidi Allen.

Change UK was founded in February by lawmakers leaving the Conservatives and Labour. It backs a new referendum that could overturn Britain's decision to leave the EU.

It had a disappointing result in last month's European Parliament election, securing just 3% of votes, as pro-EU voters supported larger pro-European parties.

New leader Anna Soubry said Tuesday she was "deeply disappointed that at such a crucial time in British politics our former colleagues have made this decision."

The six departing lawmakers said they would be "supporting each other as an independent grouping."