Change UK has applied to the Electoral Commission to change its name following a dispute with the petitions website Change.org.
The party has written to the elections watchdog asking to be renamed The Independent Group for Change.
It says Change.org is threatening to sue its MPs unless the party alters its name by 15 June.
Change UK – originally called the Independent Group – was formed in March by former Labour and Tory MPs.
In a statement, the party said it had agreed not to use the name permanently before May’s European elections after the threat of personal legal action against its MPs, as it had “no time left to register a new party name”.
It said it had since asked Change.org for more time to find a solution, but the website insisted the party must choose a new name “without delay”.
The party registered as Change UK in April, when its application was approved by the Electoral Commission, although its favoured logo was rejected.
It lost lost six of its 11 MPs earlier this month following a disappointing performance in the EU elections, when it failed to get a single MEP elected.
The party announced that Anna Soubry had been elected new party leader after its interim leader, Heidi Allen, was among those who quit.
Along with Ms Soubry – a former Tory minister – the remaining Change UK MPs are Chris Leslie, Joan Ryan, Mike Gapes and Ann Coffey.