The founder of the Sharia Watch pressure group is launching a bid to be the next UKIP leader on Saturday.
Anne Marie Waters was blocked from standing for UKIP at the election, with then leader Paul Nuttall saying her views made him “uncomfortable”.
She campaigns against Sharia law in the UK and has called Islam “evil”.
UKIP said the campaign launch was “not in any way an official UKIP event” and urged members to “think very carefully” before attending.
A UKIP spokesman said all leadership candidates would be vetted by the party’s National Executive Committee, who will decide which ones will be allowed to go forward to a vote of the membership.
Waters had planned to launch her leadership bid at Rotherham football club but has been forced to find an alternative venue.