More than 15,000 houses stretching from Bedford to Milton Keynes could be built in the next eight years if a new Government proposal gets the go-ahead.

Two new eco-towns – Marston Vale and New Marston – would be built on greenfield and brownfield land to the south of Bedford, engulfing villages such as Stewartby and Marston Moretaine.

Marston Vale is one of 15 areas shortlisted by the Government, which plans to build ten eco-towns in England by 2020.

The new towns would be built between the outskirts of Bedford and junction 13 of the M1, on sites including the former Kempston Hardwick brickworks and alongside the Marston Vale railway. An extension of The Wixams development. would be included.

However, the Campaign to Protect Rural England (CPRE) has said such a large development would destroy what little green space is left.

Ann Collett-White, from CPRE's Bedfordshire branch, said: "The scale of this town is huge and comes on top of the housing that the county has been asked to allocate through the regional planning process.

"The Marston Vale is already the target of enormous numbers of opportunistic applications from big developers.

"An eco-town, in addition to many of these other proposed developments, would create one massive wall to wall development and not many trees for the forest.

"What will develop is one long sprawl of low-density interconnected housing between Bedford and Milton Keynes, something which the CPRE has long feared."

The Government has said the new towns should achieve zero carbon standards, and include a secondary school, medium-sized shopping centre, good quality business space and leisure facilities.

Between 30 and 50 per cent of each town's housing would be 'affordable', with a particular emphasis on larger family homes.

But doubts have been raised about whether Bedford has the infrastructure to cope with another 15,400 homes.

Nadine Dorries, Conservative MP for Mid Bedfordshire, said: "My main concern is the need for substantial investment in new infrastructure such as improved roads, better transport links and enhanced public transport.

"Eco-towns need eco-infrastructure at the same time, to prevent people spending hours of their time stuck in traffic jams, as they try to get to their carbon neutral homes.

"I am all in favour of moves to tackle the challenge of climate change, this is why I am calling on the Government to take a more joined up approach to this issue."

Bedfordshire County Council, which will cease to exist next year, has provisionally backed the plans.

Coun John Scott, cabinet member for planning and economic growth, said: "A critical requirement we want to see with the eco-town planning process is proper consultation with all stakeholders, nearby town and parish councils and their residents.

"If this doesn't happen, then there could be real concerns that eco-towns are bypassing the planning system."

The Government plans to form an expert panel to subject each proposed site to a number of tests before the final ten locations are confirmed in the next six months.