Banks making massive profits should hand over cash to tackle London's gang problem, Conservative mayoral candidate Boris Johnson says.

Mr Johnson said he planned to create a "Mayor's Fund" to channel money from the financial sector to volunteer groups.

The plan comes a week after Lambeth Council published a report saying the borough was home to a quarter of London's gangs, with more than 2,500 members.

Mr Johnson said he wanted companies and people benefiting from London as the world's financial centre to give something back.

But Mayor Ken Livingstone's campaign team said Mr Johnson's scheme would raise only a small percentage of the £78million the mayor has committed to youth services across London.

Liberal Democrat mayoral candidate Brian Paddick said City Hall needed a proper audit itself before it asked business for money.