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.
“There were concerns about my ‘views’ and no doubt, police were happy to add to such concerns”, she said in a statement on her website.
South Yorkshire Police has said the decision to cancel the event at Rotherham’s New York stadium was taken by the club.
The launch will now take place at an undisclosed location in Rotherham. Waters took part in a “silent protest” march against grooming gangs in the town last year.
In a joint statement, UKIP MEP Jane Collins and councillor Allen Cowles, leader of UKIP’s Rotherham branch, said they supported the decision to cancel the planned stadium rally and urged the party’s councillors to boycott Waters’ campaign launch.
Mr Cowles said: “UKIP councillors wish to make it clear that they do not condone in any way the views Ms Waters has previously expressed, or what she stands for.”
Waters announced her plans to stand for the UKIP leadership at a rally in Manchester earlier this month, where she was introduced by former English Defence League leader Tommy Robinson.
She told the cheering crowd “Islam is a killing machine” and urged them to “join UKIP and vote for me,” adding that the party will “try to stop me”.
Analysis by BBC Political Correspondent Alex Forsyth
After the Brexit vote, UKIP’s leadership was aware the party had to broaden its appeal.
The former leader, Paul Nuttall, backed a radical policy platform with social integration at its core.
He said the party would shape the debate around extremism and Islamism in the way it claimed to have done with immigration – daring to address topics other politicians wouldn’t.
But while some in UKIP welcomed the policies announced in the election manifesto – including a ban on face coverings – they caused disquiet among other members who feared the party was in danger of being seen as Islamophobic.
Mr Nuttall insisted that was not the case, saying the focus was breaking down barriers in society and improving integration.
But UKIP is sensitive to public perception about its policy and direction. Having been dogged by allegations of racism in the past, it’s determined not to go there again.
A former Labour Party activist, Waters set up a UK branch of anti-mass immigration organisation Pegida with Robinson, but is no longer thought to be involved with the group.
She founded Sharia Watch UK, which aims to “to document the advancement of Sharia law in Britain,” in 2014.
She hit the headlines a year later when she announced plans for an exhibition of cartoons of the Prophet Muhammad, but was forced to cancel the event after police warned it could be “a risk to public safety”.
She has argued that UKIP could regain support if it had the “guts” to be “honest about Islam” and challenge the view that it has “nothing to do” with jihadist violence.
Anti-fascist campaign group HopeNotHate has branded Waters a “toxic figure” and urged UKIP to expel her from the party.
But she has been defended by former UKIP leadership contender Raheem Kassam, editor of the Breitbart London website, who wrote earlier this year: “If UKIP ditches Anne Marie Waters, the party is over”.
‘Beyond party policy’
The UKIP leadership contest was triggered by the resignation of Paul Nuttall, when the party failed to win any seats at the general election and saw its share of the vote collapse.
Mr Nuttall, who campaigned for a ban on burkas and Sharia courts, said in April that Waters’ comments were “way above and beyond party policy” and some had made him feel “a bit uncomfortable”.
London Assembly member Peter Whittle and Ben Walker, a former UKIP councillor in South Gloucestershire, have also announced leadership bids.
MEP Bill Etheridge, who came third in the first of UKIP’s two leadership contests last year, and Thanet council leader Chris Wells have both said they might stand if Nigel Farage cannot be persuade to return to the job he quit after last year’s Brexit referendum.
The former UKIP leader has not ruled out a bid.