The organisers of a Ukip youth conference have said they were forced to cancel the event because of “hard left” threats.

Anti-racism group Stand Up to Racism had planned to demonstrate outside the Hilton Hotel in Sheffield, where the Young Independence conference was due to take place over the weekend.

But the hotel cancelled the event, leading Ukip to attempt to secure other venues, which also declined their booking.

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The Young Independence Executive Council accused the “far left” of sending “threats of violence” to venues if they hosted the conference, adding that the emails branded “Ukip as ‘far right’, ‘fascist’ and ‘Islamophobic’ to name a few.”

The conference has now been cancelled or postponed indefinitely, the council said in a statement to members.

It would have featured Martin Sellner, the Austrian leader of the far-right Generation Identitaire movement, along with Anne Marie Waters, Ukip leadership candidate and former leader of anti-immigration group Pegida in the UK.

Ukip was also forced to cancel a planned three-hour river cruise from Sheffield.

Key Faces of UKIP Show all 11 1 /11 Key Faces of UKIP Key Faces of UKIP Nigel Farage Getty Key Faces of UKIP United Kingdom Independence Party (UKIP) Migration spokesman Steven Woolfe addresses supporters and media personnel in central London Getty Key Faces of UKIP Robert Kilroy-Silk, former television presenter and newly elected member of the European Parliament for the UK Independence Party (UKIP), shows a placard against the European Constitution in front of the Houses of Parliament Getty Key Faces of UKIP Mark Reckless, Director of Policy Development addresses party members during the UK Independence Party annual conference at Doncaster Racecourse Getty Key Faces of UKIP Gerard Batten MEP poses with protesters outside parliament Creative Commons Key Faces of UKIP Diane James gives an address at the UKIP Autumn Conference in Bournemouth Getty Key Faces of UKIP Douglas Carswell MP speaks to party members and supporters during the UK Independence Party annual conference Getty Key Faces of UKIP Suzanne Evans, Deputy Party Chairman of UK Independence Party (UKIP) speaks during the launch of UKIP's election manifesto Getty Key Faces of UKIP Peter Whittle, the UK Independence Party Member of the London Assembly, is interviewed in central London Getty Key Faces of UKIP MEP Mike Hookem during a visit to Concept Metal Products & Co Ltd Getty Key Faces of UKIP Paul Nuttall, Deputy Leader of the UK Independence Party speaks at a Say NO, Believe in Britain debate at Carn Brea Leisure Centre in Pool near Redruthon Getty

In a statement, Sheffield Stand Up to Racism said: “We are grateful to all the venues who declined the booking from Young Independence, the youth wing of Ukip, rejecting the party’s racism, Islamophobia and hate.”

The statement added: “Stand Up to Racism and other anti-racists will continue to challenge racism and the far right at all times and will always be prepared to stand up to Ukip’s backward and divisive policies.