Campaign group Change.org UK is seeking legal advice over the rebranding of The Independent Group as 'Change UK'.
The group announced today it was applying to be a political party to stand in European elections, under the nambe 'Change UK - The Independent Group'.
However they may now face legal action from Change.org, which offers a platform for users to organise petititions and campaigns.
A Change.org spokesperson said: "Change.org UK or @UKChange as we are interchangeably known, is totally independent of party politics, always has been and always will be.
"It is said that imitation is a form of flattery. But the movement that we have built in the UK to win campaigns for ordinary people is ours - all 17 million of us. We are seeking guidance on the proposed use of our brand name by those reported to be setting up a new political party."
Change UK - The Independent Group has appointed former Conservative MP as intterim leader.
Ms Allen said: "Today marks a huge step forward on The Independent Group's journey to becoming a fully-fledged political party, so I am delighted to have been chosen as our interim leader.
"If we are to deliver on our ambition to change politics for the better, it is vital that we attract support from people from every walk of life, every political background and none.
"We in Change UK, as we hope to be known, don't just dream about a fairer and better future for our country, we are determined to unleash it through hard work, passion and shared endeavour."
The UK will have to stage elections to the European Parliament as a condition of any further delay to Brexit.
Defeat for Prime Minister Theresa May in a vote on her Withdrawal Agreement in the House of Commons on Friday would greatly increase the likelihood of an application on April 12 for a long extension to the Brexit process.
In order to stand candidates in the European polls, conducted on a regional proportional representation system, any group must be registered as a political party with the European Commission.
The Independent Group was founded by former Labour MPs Luciana Berger, Ann Coffey, Mike Gapes, Chris Leslie, Gavin Shuker, Angela Smith and Chuka Umunna on February 18.
They were later joined by Labour defector Joan Ryan and ex-Tories Anna Soubry, Heidi Allen and Sarah Wollaston.