Petition website Change.org is taking legal advice after accusing MPs in the Independent Group of "using our brand name".
The campaigns corporation warned it could take action after the 11-strong group of MPs announced they are setting up a full political party called Change UK.
And the 'TIG' MPs rubbed salt into the wound when Anna Soubry, one of the 11 MPs, accidentally referred to her new party as Change.org.
A source at the campaign website said chiefs are now taking legal advice and contacting the Electoral Commission to see what can be done.
A spokesman said: "Change.org UK or @UKChange is a movement of 17 million people in the UK.
"We empower ordinary people to start petitions and campaign to create the change they want to see.
Independent Group registering as political party called Change UK
"Our petition starters, like Laura Coryton who ended the tampon tax and Richard Ratcliffe who is fighting for the freedom of his wife Nazanin, are disrupting the status quo of power in politics.
"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."
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The group of 11 MPs who broke away from the Tories and Labour will stand in European elections - if they happen.
And in order to register they have had to choose an interim leader - former Tory MP Heidi Allen will fill the role.
They have also had to submit a logo and draft constitution to the Electoral Commission who will rule on if they can become a party in the coming weeks.
Commenting on the application Heidi Allen MP 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."
