A culture of "impunity, racism and genocidal tendencies has overtaken Israeli society", according to Palestinian boycott activist and author Omar Barghouti.

Mr Barghouti was speaking in support of a boycott motion proposed at a London Literature Festival debate at the Southbank Centre on Sunday.

He was joined by Seni Seneviratne, a British-Sri Lankan poet who is a member of British Writers in Support of Palestine, in backing the motion, which questioned whether a cultural boycott could be a "viable and effective political strategy; indeed a moral imperative".

Mr Barghouti said: "Israel uses culture to brand itself and change its image around the world. Boycott is the most effective non-violent means available to us to end the occupation and apartheid."

Ms Seneviratne compared Israel to apartheid South Africa and said the boycott was "forcing Israeli journalists and politicians to recognise the shift in world opinion".

American writer Carol Gould, opposing the motion alongside JC and Guardian columnist Jonathan Freedland, challenged the comparison. She said: "If Israel is an apartheid state how is it that Omar has been able to study at Tel Aviv University? Did blacks study at Wits [in Johannesburg]?"But both Ms Gould and Mr Freedland were repeatedly shouted down by pro-Palestinian activists.

A clearly shaken Mr Freedland told the audience: "Tonight has been hugely revealing. I thought my disagreement with the boycott movement was because I want to see the end of occupation and you want to see the end of occupation and it was an argument about tactics.

"What has come through loud and clear is your motivation is not actually just the end of occupation but it's with Israel itself - you have a fundamental problem with it."