The Environment Agency says it is "extremely concerned" about the dumping of old tyres.

The BBC's Margaret Gilmore: "The tyres cause pollution in the air and in rivers"

It fears that a massive predicted increase in the number of tyres used, combined with a forthcoming ban on one of the main ways of disposing of them, could be "a recipe for disaster".

The UK discards 37m used tyres every year. Laid side by side, they would stretch from London to Sydney.

Vehicle numbers are creeping inexorably upwards

And if they were piled together, they would fill the entire Millennium Dome.

The number of tyres in use is forecast to increase by up to 60% by 2021, as the number of vehicles rises.

Between 1970 and 1996 road traffic more than doubled in Britain, from 200bn to 440bn vehicle kilometres a year.

A new directive from Brussels is expected soon to ban the disposal of tyres in landfill sites.

The agency says it is afraid that illegal tyre dumping may increase significantly.

Its Chief Scientist, Dr Jan Pentreath, says: "Illegally dumped tyres are a real environmental problem - they are a fire risk and an eyesore.

"Tyre fires cause serious pollution, with black smoke contaminating the air, soil and plants. In Powys, a tip containing 10m tyres has been burning continuously for nine years."

The agency, which says it does not disagree with the European Union decision to ban sending tyres to landfills, makes several recommendations for tackling the problem.

It says: