BedZED in Surrey is a current example of an eco-development

The restriction is among proposals designed to minimise the environmental impact of the settlements.

Government sources say the new town centres are to be car-free, and the 15mph limit will be enforced on "key roads" leading into them.

Environmental protesters have criticised the scheme for focusing too narrowly on carbon emissions.

'Revolutionary living'

More than 50 bids to create the zero-carbon developments have been entered by companies.

Housing minister Caroline Flint will set out standards expected of them later this week and the announcement of the shortlist of 10 new towns is expected in the coming weeks.

Ms Flint said: "These developments will be exemplars for the rest of the world, not just the rest of the country. It's critical that we get it right - and I make no apology for setting the bar as high as possible.

"We have a unique opportunity to deliver a programme which will genuinely revolutionise the way people live."

Ms Flint has said she wants to see towns designed around pedestrians, cyclists and public transport users.

Protests

Environmental protesters say the plans do not give adequate consideration to other ecological issues, such as the impact building would have on wildlife.

Up to five eco-towns are expected to be built by 2016, and up to 10 by 2020.

They will have populations of around 5,000 to 20,000 and be linked to larger towns and cities.

There have been nationwide protests over the plans from residents who claim the schemes will put too much pressure on local services.

Opposition has been voiced in places such as Grovewood in south Derbyshire and Stoughton in Leicestershire.

Last month around 300 campaigners marched against plans for a 6,000-home development in Long Marston, near Stratford, Warwickshire.