Konstantin Kisin was presented with the “behavioural agreement form” alongside an invitation to appear at a fundraising event organised by Unicef on Campus at SOAS University of London.

It said: “By signing this contract, you are agreeing to our no-tolerance policy with regards to racism, sexism, classism, ageism, homophobia, biphobia, transphobia, xenophobia, Islamophobia or anti-religion or anti-atheism. It does not mean that these topics cannot be discussed. But it must be done in a respectful and non-abusive way.”

Kisin, who grew up in the Soviet Union and was recently named joint New Jewish Comedian of the Year at the UK Jewish Comedy Festival, told The Times that the contract represented “a threat to freedom of speech” and he had “declined the invitation on a point of principle”.

He added: “When I saw this letter, basically telling me what I could and couldn’t say, I thought this was the kind of letter a comic would have been sent there.”

A spokesperson for SOAS Students Union said the Unicef on Campus society had been “overzealous” in applying Charity Commission guidelines.