The Liberal Democrat candidate for Mayor of London today pledged to cut crime in the city by 20% if elected.

Brian Paddick named improving public transport and increasing affordable housing as other key priorities.

His launch event was held in Brixton, south London, this morning. Newly elected Lib Dem leader Nick Clegg attended, calling Mr Paddick an achiever and “serious, focused and determined.”

He was the UK’s most senior out gay policeman until his retirement as Deputy Assistant Commissioner of the Metropolitan Police in May 2007.

The 49-year-old faces incumbent Ken Livingstone and Tory candidate Boris Johnson in May’s election.

Mr Paddick came to public prominence as borough commander of Lambeth, when his policy of targeting resources at class A drug dealers and taking a more relaxed approach to cannabis use caused right-wing outrage.

Today he said that if elected he would cut crime by 20% during his first term or stand down.

“I am not a career politician. I care about delivering the real changes that Londoners will notice,” he said.

I have a track record of performance against Londoners’ number one concern: crime.

“Ken Livingstone has said he cannot do anything about gun and knife crime.

“Boris Johnson has admitted he doesn’t have the experience to deal with it.

“It’s time for someone who can stop the slaughter on our streets.

“I will make tackling crime in the capital a priority. I will cut crime in London by 5% every year over the course of my first term in City Hall.

“And I will take personal control of ensuring this target is met by chairing the Metropolitan Police Authority. If I fail to reach my target after four years, I will not stand again.

“Too many innocent lives have been lost. It’s time for a radical change. It’s time for someone who will deliver.”

Mr Paddick’s eye-catching pledge of a 5% cut in crime each of the four years of the Mayor’s term of office will be measured according to the British Crime Survey and official police figures.

The BCS, described by the Paddick team as “the most reliable measure of crime,” interviews 40,000 people in England and Wales about their experiences of crime and therefore includes those crimes that have not been reported to or recorded by the police.

Last year the BCS was criticised for under-estimating the amount of crime in England and Wales. The number of times a victim can be targeted by an offender is capped at five incidents a year.

Mr Paddick also proposed a ban on all cars in central London at today’s launch event and pledged to improve Tube and bus reliability.

A YouGov poll for ITV’s London Tonight at the start of 2008 found that of those would are going to vote and have made up their minds, 45 per cent intend to vote for Ken Livingstone, 44 per cent for Mr Johnson and just 7% for Mr Paddick.

However, it is thought that many Londoners have not yet decided if they are going to vote or who to vote for.

In the London Tonight poll 68 per cent of respondents mentioned crime as the top issue in terms of deciding who to vote for.