LONDON - LONDON'S mayor, Boris Johnson, launched an expletive-laden attack on a ruling party lawmaker after being criticised for giving confused evidence to a parliamentary committee, reports said on Thursday.

Johnson, a member of the main opposition Conservatives, reportedly accused committee chairman and Labour MP Keith Vaz of talking 'bulls***' and making him look like a 'f***ing fool' in a heated telephone call last week.

The Evening Standard newspaper said Johnson - well-known for his gaffes, his affable nature and his messy white hair - also accused Vaz of 'f***ing smear tactics' on behalf of Prime Minister Gordon Brown's Labour party.

Details of the conversation were leaked after Mr Vaz circulated a transcript he had made - apparently without Mr Johnson's knowledge - to committee colleagues.

Mr Johnson's office disputes the transcript, saying the mayor had 'made his points forcefully and once or twice used strong language' in a conversation that he regarded was private.

The mayor - who is directly elected - had telephoned Mr Vaz on Feb 4 to complain after the lawmaker appeared on television questioning Mr Johnson's evidence to the committee the day before and saying it contained discrepancies.

Mr Vaz's committee was investigating the arrest of a senior Conservative politician, Damian Green, over the alleged leak of government information.

Mr Johnson, as head of London's police authority, was asked when he first raised the arrest with Conservative leader David Cameron. The committee claims he offered four different accounts, having failed to properly prepare.

The mayor insists he was cooperative and courteous towards the committee. -- AFP