Boris Johnson looking forward to UK 'Independence Day'

Boris Johnson is a leading advocate of leaving the European Union. Credit: ITV News

London's mayor Boris Johnson has said if Britain votes to leave the European Union in the referendum on June 23, the next day would be the UK's "independence day".

Mr Johnson, who is a leading advocate of leaving the EU, told ITV News the bloc was "out of date" and "had run its course".

He added: "I think that it would be a massive tonic for this country, and for British business (to vote to leave), and a chance to escape an ever more constricting, oppressive and economically-doomed structure".

Speaking about the resignation of John Longworth as director general of the British Chambers of Commerce, Mr Johnson said it was "very sad" that he had been "effectively gagged" over his ideas about the EU.

But he added that he was glad that Mr Longworth believed the UK could have a brighter future outside the union, and believes he may now officially join the 'leave' campaign, saying: "I think what will happen now is that he will join our movement and speak his mind. I hope very much that he will."