About 500 protesters waving placards including "Down with the eco-town" and "Stop the Co-op eco-town" attended the rally in Stoughton, Leicestershire.

The village and surrounding area is on a list of about 50 sites that have been ear-marked by developers as possible locations for one of the Government's new eco-towns. It is expected that the Government will cut down the number of sites to a shortlist of 18 next week.

The Co-op owns about 4,500 acres of farmland around Stoughton and there are plans to build about 15,000 homes on part of the land in a development which campaigners say would dramatically alter their community.

Edward Garnier, the Conservative MP for Harborough, said: "This site creates a very easy deal for the Government because it only has to deal with one landlord whereas with other sites it will have to deal with several different land-owners.

"The reason why (Saturday's) demonstration was important is that we are trying to bring to national attention the complete idiocy of this proposal. It will not only damage rural Leicestershire but Leicester. There won't be the roads, the nearest motorway is 30 miles away. The whole thing is a disaster."

A final decision on the locations of the eco-towns is expected in the summer.

The idea behind them is that they are environmentally friendly, with public transport links and energy efficient homes.

Kevin Feltham is chairman of the campaign group Campaign Against Stoughton Co-op Eco-Town and a county councillor for Leicestershire. He said: "(The) rally was very successful. They have got to realise that people aren't very happy about it. They will have to build a huge amount of stuff and even if they build the roads to the city, the county council estimates it would cost hundreds of millions of pounds to build access to the M1."

He added: "This is just the wrong place. The impact on the community would be devastating. I am sure there are plenty of brownfield sites that would be fine. This isn't just one or two people saying 'not in our back-yard' - all our MPs, the city council and the county council agree."