Congestion charging was introduced in February 2003

According to the survey the volume of traffic on the roads has reduced by 15% and congestion has been reduced by 30% since the toll was introduced.

Insurance company More Than said the scheme was so successful it should be extended around the UK.

But a Met Police spokeswoman said there were a number of factors which could have influenced the figures.

'Tax on people'

"Road traffic accidents where people were killed or seriously injured were down by 20% last year," she said.

"There are many factors which could have influenced those figures. The charge does lead to less congestion on the road but it also leads to traffic going at faster speeds, so both factors have an impact."

She said it was difficult to provide figures for accidents within the congestion zone, as smaller incidents often went unreported.

Congestion charging was introduced in February two years ago with an average of 10,000 people now paying the charge each day.

David Pitt, head of More Than, said: "From our research we can see that the London congestion scheme has had a positive impact in significantly reducing the number of accidents on the road in the charging zone."

Michelle Wininger, of the West London Residents' Association, is campaigning to stop the toll being extended into west London.

"I don't believe the congestion charge has got anything to do with safety, it's about another tax on people, many of whom can't afford to pay," she said.