Ken Livingstone has renewed his commitment to bear down on gun and knife crime in London with a call for tougher sentencing and bail conditions for those caught carrying these weapons.

Speaking in south London on Wednesday, the mayor said that while gun-enabled crime in the capital was falling, Londoners were still rightly concerned about serious violent crime involving young people and the problem of gangs.

Metropolitan Police figures show that the total number of gun-enabled crimes in London has fallen by more than 20 per cent in five years - from 4,444 offences in 2002 to 3441 in 2007.

Mr Livingstone proclaimed that in order to see these numbers drop even further, a range of different solutions was required.

'We have to start with good intelligence and effective targeted operations against known criminals and gang members. That is what the Met are doing and this programme of action will be intensified with whatever extra resources are needed," he said.

'On top of the action that will be taken by the Met against gangs, I want to see tougher sentences and bail conditions. 'I believe there should be tougher sentences still for the carrying and use of knives and that shopkeepers proven to have sold knives to those underage should know they will face the prospect of a prison sentence.

The Mayor said he backed a petition calling for tougher sentences that was submitted to the Prime Minister by the family of 16-year-old Kodjo Yenga, who was stabbed to death in Hammersmith last year.

He reiterated plans for his London Youth Offer, a £79m programme of investment over the next two years in new centres, facilities and activities for young people. He also pledged to maintain and increase the Youth Offer over the following two years.

Mr Livingstone also took the chance to lay into rival Boris Johnson, claiming that his voting in Parliament against Labour's mandatory five-year sentences for gun possession showed that the Tory candidate could not be trusted to deal with crime in London.

"His approach is waffle, not action," said Livingstone.

According to a poll, Johnson's lead in the London Mayoral race has more than halved over the past week.

The latest research by YouGov for the Evening Standard showed Johnson ahead of Livingstone by just six points, suggesting that the outcome of the May 1 election is still far from certain.

The poll put Mr Johnson on 45 per cent compared with 39 per cent for the current mayor.