Oxford MP Evan Harris has defended the Oxford Union's controversial decision to invite a convicted Holocaust denier and the leader of the British National Party to speak at a student event tonight.

Dr Harris, Liberal Democrat MP for Oxford West and Abingdon, rejected claims that asking David Irving and Nick Griffin to take part in a debate on free speech gave them an undeserved aura of respectability.

The MP, who has himself agreed to take part in tonight's Union debate, told BBC Radio 4's Today programme: "Free speech is not a privilege, it's a right.

"If I want to debate the limits of free speech within the law I can't really do that consistently by no-platforming extremists.

"I don't want a bunch of students telling other students or my constituents or me who I can talk to within the law because that way lies effective despotism."

Dr Harris described the two men as "unpleasant" and their far-right views "wrong" and "horrible".

But he said that no-platform policies led to unwelcome restrictions to free speech. When he was an Oxford University student, in 1986, such a policy led to right-wing Conservative MPs being banned from speaking events, he said.

He added: "It's reasonable within a university for a debate to be had about the limits of free speech."

Tonight's event has been condemned by Oxford East MP Andrew Smith.