Tory leader Michael Howard attended Mr Norris's manifesto launch

Mr Norris made the statement as he launched his election campaign at the Arden Estate, in Hackney, east London.

Labour candidate Ken Livingstone also began his campaign on Thursday, with Lib Dem Simon Hughes unveiling his mayoral manifesto last week.

The three will be among those standing for the position on 10 June.

Mr Norris accused incumbent mayor Mr Livingstone of "frittering away" his chance to reduce crime.

If crime is not lower and people in London do not feel safer by the end of my first four years, I will simply not re-stand Tory mayoral candidate Steve Norris

He said: "People simply don't feel safe on London's streets.

"With murder and violent crime rising relentlessly, I am determined to make the changes that will actually reduce crime across London - from the inner city estates to the leafy suburbs.

"I make one simple pledge: If crime is not lower and people in London do not feel safer by the end of my first four years, I will simply not stand for re-election."

In an attempt to adhere to his pledge of less crime, Mr Norris said he would put more of London's 30,000 police on the street and bring in zero-tolerance for anti-social behaviour.

This would include cracking down on illegal mini-cabs, vandals and graffiti-artists.

'Scrap congestion charge'

Mr Norris said he would be drawing upon the example of former New York mayor, Rudy Giuliani, and planned to bring his team to London if successful in the elections.

There would also be more police and security guards on buses, tubes, trains, and at isolated suburban stations.

Mr Norris also wants to scrap the congestion charge and introduce free buses for primary school children.

Conservative leader Michael Howard attended the launch.

Following the start of the campaign Ivan Massow announced he was rejecting his plan to stand as an independent mayoral candidate and rejoining the Tory Party.

The businessman famously defected to Labour after accusing the Tories of dithering over gay rights.

But he said there was "no alternative" to the revitalised Tory Party under new leader Michael Howard.