Both Ken Livingstone and Boris Johnson have pulled out of a BBC mayoral debate in protest at being asked to share a platform with the British National Party.

The Labour Party candidate for London Mayor said that the far right wanted to "destroy our democracy and stand for the elimination of our basic rights" and had long opposed giving them a platform to express their views.

Diary clashes meant Johnson had not confirmed he would take part in the radio debate, but although a slot had been left open for him to attend, his aides confirmed on Friday evening that he would not share a platform with the BNP.

Livingstone insisted that the BNP "cannot be treated as a legitimate part of politics," adding: “I am withdrawing from Monday’s mayoral debate on BBC London 94.9 on the grounds that I am not prepared to share a platform with the British National Party," he said.

‘We have been in negotiation about a debate with the main candidates for BBC London 94.9 – but only now have we been informed that the BNP had been invited to take part in this debate, and this has been confirmed to us today.

“I will not share a platform with the BNP and it is a point of principle to me that I never will do."

On Friday it was reported that the BNP candidate for mayor, Carlos Cortiglia, had said he would be giving his second preference vote to Livingstone - an endorsement that the former Labour mayor hasn't welcomed.

“That the BNP candidate may have called for a second preference for me is clearly designed to disorganise progressive opinion and divide opposition to them," Livingstone said.

"Not only don’t I want their second preference but I will not share a platform with them. I urge everyone to use their vote on 3 May to vote to keep the BNP out."

According to the Mayor Watch website Green candidate Jenny Jones has also withdrawn from the debate.