Liberal Democrat MP Lembit Opik has defended his decision to take part in a public debate with the leader of the far-right British National Party.

No one is stopping the BNP running for office, but I would say it is a grave mistake for mainstream democrats to give them political credibility

Martin Salter, Labour MP

Mr Opik denied he had been disowned by his parliamentary colleagues after agreeing to appear alongside Nick Griffin, a constituent of his, in a debate on extremism.

The event at Cambridge University was cancelled by the organisers at the last minute amid concern about violence outside the venue.

Labour students and anti-racism campaigners at the university argued the BNP would use the platform to stir up race hate.

But Mr Opik said he had no regrets about agreeing to take part.

'Oxygen of publicity'

He told BBC 2's Westminster Live: "I simply do not understand why people feel that we can prevent the BNP winning hearts and minds if we are not willing to challenge them directly in debates like today.

Salter: Speaking out against BNP

"I wasn't looking forward to the debate but I do feel that once again we have patronised the people in Cambridge University who surely would not have been convinced by the BNP arguments."

He said he did not believe the BNP's arguments would "stand up to scrutiny" in a head-to-head debate.

And by tackling them in this way, he would "reduce the likelihood of them winning more seats".

He admitted he was giving the far right the oxygen of publicity "to some extent".

But, he added, "I think that oxygen is more likely to poison the BNP rather than to give them breathing space to develop."

'Convicted criminals'

Mr Opik's comments were dismissed as "naive egomania" by Labour MP Martin Salter.

He added: "No one is stopping the BNP running for office, but I would say it is a grave mistake for mainstream democrats to give them political credibility."

He said Mr Opik would be disowned by his own party - a claim denied by Mr Opik.

The Lib Dem MP said he had checked with party leader Charles Kennedy before agreeing to take part in the debate.

'Controversial'

The meeting had been due to be held at the premises of the Cambridge Union, after organisers - and rival debating society - the Cambridge Forum was refused the use of venues elsewhere.

We certainly did not think there would be a risk of violence

Chris Paley, organiser

Demonstrations had reportedly been planned by the Anti-Nazi League, the university Jewish society and its Muslim society.

Katy Long, editor of student newspaper Varsity, said: "This meeting has been a hugely controversial issue among students.

"Opinion seems to be split half and half between the freedom of speech lobby and those who think he should not be allowed to speak."

She added: "Nick Griffin is a Cambridge graduate and there is a feeling that we don't really want to be endorsing his views."

A spokesman for the Cambridge Student Union said it had also been opposed to the debate.

'Out of order'

Chris Paley, president of organisers the Cambridge Forum, said he had decided to call the debate off after consultation with the police about the risk of violence.

He said it was "out of order" that violence had been allowed to stifle democratic debate.

"If we are going to have a debate about extremism it is important to have both sides," he told BBC News Online.

He said the Forum had decided to invite Mr Griffin to take part "because of his growing influence."

He added: "We certainly did not think there would be a risk of violence.

"When you use violence to stop free speech it is absolutely against democracy."

'Vulnerable students'

He added: "I don't go with this argument that you get legitimacy by appearing and giving a talk to people.

"What gives you legitimacy is winning the arguments."

Ellie Reeves, national chairwoman of Labour Students, who had campaigned against the event, said: "This proposed debate was not just a harmless academic exercise.

"Vulnerable students feel threatened by the BNP and Nick Griffin's extreme views and they should not be given credence in the way Lembit Opik was proposing."