Plans to develop sites in England into housing as "eco-towns" are drawing protesters to parliament, as a second round of consultation on the issue is launched. But why is the idea controversial?
What is an eco-town?
The idea has drawn strong protest
The term refers to the government's idea for planning new housing in England that it says is needed to meet demand and could be created in an environmentally conscious way.
Gordon Brown has said housing is a priority.
In July 2007, the government set out proposals that an eco-town should be:
A small new town of at least 5,000 but up to 20,000 homes
A place with a separate, distinct identity but good links to surrounding towns and cities in terms of jobs, transport and services
A zero-carbon development where the town would put back as much or more energy than it uses to the national grid. It should also excel in at least one area of environmental technology
Equipped with infrastructure that includes a secondary school, shopping, business space and leisure
Housing stock should be 30-50% affordable housing with a good mix of tenures and size of homes in mixed communities
The scheme should be overseen by a delivery organisation to manage the town and its development and provide support for people, businesses and community services
Where and when will they be built?
Sites were originally suggested by developers and landowners. In April, 57 potential locations were shortlisted to 15, including some former military and industrial sites.
They are spread across England and include places in South Yorkshire, Nottinghamshire and Oxfordshire.
The government wants to build a maximum of 10 in total, and a list will be finalised later this year.
Housing Minister Caroline Flint is taking forward plans to build five eco-towns by 2016, the remainder by 2020.
How would you spot one?
No-one yet knows how an eco-town would look, or show off its green credentials, but similar development ideas in other countries have put more emphasis on green spaces, renewable energy sources and sustainable transport solutions such as cycle-friendly roads.
Developers and politicians could look to examples overseas including Freiburg, Germany, where environmentally-friendly homes are promoted, or the Hammarby Sjostad area of Stockholm, Sweden, where tougher environmental requirements have been placed on development.
Closer to home, there is the Findhorn Foundation in Scotland.
Isn't this just development under another name?
Yes, argue the critics. The Campaign to Protect Rural England (CPRE) was initially sympathetic to the idea of building to high environmental standards while providing affordable homes.
But it has turned against the firmed-up proposals, saying many of the shortlisted schemes are former failed development schemes, chosen by the developers themselves and running against local development plans.
It has a number of concerns, including worries that new towns are "the least sustainable way" of developing housing, the use of greenfield sites and a lack of evidence that they would be sustainable places to live and work rather than commuter suburbs.
Earlier in June, a panel set up by the government to look at the plans found some schemes were not much better than housing estates with green edges added.
The Eco-Towns Challenge Panel of housing and transport experts said developers had much work to do.
And the Conservative opposition says current planned developments are so poor that the party will withdraw its support from the process. Eco-towns are "dead in the water", it says.
But the government continues to back the plans. On Monday, it argued the general public supported eco-town development - 46% of adults supporting the idea, while 9% against, it said a YouGov survey found.
This changed to 34% support and 15% opposition when people were asked if eco-towns should be built within five miles of their home.
What is the consultation protest?
The government's first stage of public consultation ends on Monday.
In the government's second phase of public consultation, roadshows will take place around the shortlisted sites, sustainability assessments carried out and a draft planning policy statement released.
In autumn 2008, the final shortlist of potential eco-towns will be released in the government's third stage of the process. Then local authorities will be able to consider individual schemes.