Londoners are breathing in air laced with the highest levels of vehicle pollutants since the introduction of the Clean Air Act almost 40 years ago.

The deadly cocktail - made up primarily of nitrous oxides, ozone and dust particles and which is caused by the increasing amount of traffic congesting the roads - adds to thousands of deaths in Britain each year and is worst in the capital.

The warning came from the London Air Quality Network, a group comprising the London Boroughs Association, the Association of London Authorities and the South East Institute of Public Health.

Yesterday it said the situation was getting much worse and called on the Government to introduce tolls on roads and invest in a comprehensive and effective public transport system.

It also wants to see greater encouragement given to people to walk, cycle or use buses and river launches to commute.

According to its research there are 2.2 million cars in London and 37 per cent of all journeys are made by car.

The LBA blamed ministers for failing to help to solve the capital's gridlock and said pollution levels would get steadily worse unless they took stock of the problem immediately and persuaded people to get out of their cars.

'Basically there are too many cars on the streets of London,' said its spokesman, Steve Pearce.

'We need a carrot and stick approach, the carrot being a better, more efficient, more reliable public transport system and the stick being some sort of road-pricing scheme.

'People aren't going to like having to pay more to use their cars. It's difficult to see how things will improve without a radical change of government policy.'

The Network gave evidence yesterday to the House of Commons transport committee inquiry into transport-related atmospheric pollution in London.

John Rice, director of environmental health at the South East Institute of Public Health, a voluntary body which monitors air pollution, confirmed that Londoners were now enduring the worst levels of pollution since the Clean Air Act.

That was introduced in 1956 to stem the prolific burning of coal which regularlyproduced the infamous 'pea-souper' fogs.

'That was a different type of pollution then, but now we have pollution actually discharged straight into people's faces - especially small children sitting in their pushchairs.

'We have a lot of individual sources of pollutants moving around.

'We don't yet know what are the effects of this pollution cocktail, but it has been estimated that it could influence the deaths of between 7,000 and 10,000 people per year nationwide.'

Figures for London were not available yesterday, but the capital suffers the highest levels because of the density of traffic.

Mr Pearce added that although catalytic converters are being fitted to more cars and are standard on most new models, the benefits for Londoners will be negated if pollution increases keep on climbing.

The LBA also criticised the Government for its long-standing relationship with the powerful roads lobby, many members of whom are regular contributors to Conservative Party funds.

'It has had the Government's ear for perhaps too long. Before May's local elections we were a Conservative-run organisation but even then we were saying all this to the Government,' Mr Pearce said.

The organisation has been studying traffic models of other large world cities such as Singapore and Hong Kong whose pollution levels have been reduced after the introduction of road-pricing schemes.

The Department of Transport has forecast an increase of between 35 and 59 per cent in the numbers of all vehicles by 2010 and an increase of between 45 and 74 per cent by 2015.