Protests came as the government moved to the next stage of plans
Hundreds of campaigners from many of the 15 sites in England earmarked for "eco-towns" have marched on Parliament in protest at the plans.
As the first round of public consultation ends, local authorities and pressure groups are handing in their responses.
It comes as environmental campaigners call on ministers to "go back to the drawing board" on the plans.
Meanwhile, the government is launching the next round of consultation.
It hopes to build up to 10 of the 15 shortlisted proposed eco-towns by 2020. They are meant to set new green standards in house building.
The 15 shortlisted schemes include sites in South Yorkshire, Nottinghamshire and Oxfordshire.
Up to 10 sites for the developments will be finalised later this year.
Ministers want five of them built by 2016, with the remainder completed by 2020.
The Campaign to Protect Rural England (CPRE) said new towns were "the least sustainable way" of developing housing and other plans should be examined.
CPRE head of planning Marina Pacheco said ministers should focus on one or two "truly exemplary" schemes, which were sited in the right place to be sustainable and could be developed to the best green standards.
The concerns the conservation charity have about the proposed developments include:
- The schemes risk being car-dependent housing estates
- Most are predominantly in greenfield sites, and two are in the Green Belt
- Most go against local plans agreed with communities
- The sites have been chosen by developers, rather than fitting in with planning in the wider public interest
- Lack of evidence to suggest schemes will offer truly sustainable models of living and working
- Three bids are in the east of England where, according to CPRE, water supply and sewerage have already reached maximum capacity
Ms Pacheco said that initially CPRE had supported the eco-towns initiative of building to high-environmental standards while providing the affordable homes the needed by the UK.
But she said the plans were now in urgent need of a redesign.
She said: "We are urging the government to go back to the drawing board. Many of these shortlisted schemes are recycled, failed proposals.
"But by refusing to look at alternatives, such as eco-quarters and redevelopment sites already coming through the planning pipeline, it is missing a golden opportunity."
A spokesman for the Department for Communities and Local Government (DCLG) said: "This is the CPRE reverting to type, opposing the housing that young families and first-time buyers need.
Ford, West Sussex
Hanley Grange, Cambridgeshire
Imerys, nr St Austell, Cornwall
Leeds city region, Yorkshire
Marston Vale and New Marston, Bedfordshire
Middle Quinton, Warwickshire
Rossington, South Yorkshire
Weston Otmoor, Oxfordshire
Source: Department of Communities and Local Government
"It is a shame that CPRE are preferring to perpetuate myths rather than engaging in the debate about how we build the houses we need."
Protesters are meeting shadow housing minister Grant Shapps and submitting a petition to 10 Downing Street.
The Conservatives have withdrawn their support for the plans, calling them an "eco-con".
Mr Shapps said the government had watered down the environmental standards for the construction of the towns and ignored the needs of local communities.
It was important to work with people, not against them, in order to get the housing the country needed, he said.
Among the protesters was Tony Henman, father of tennis player Tim, who opposes a development close to his village of Weston-on-the-Green, Oxfordshire.
He said: "Gordon Brown said he'd be a listening prime minister and if he's only got to listen a little bit he'll realise that he's got a thoroughly bad idea - unrealistic, unsustainable and definitely not wanted."
The first public consultation period of three months ends on Monday and Housing Minister Caroline Flint is announcing the second stage, which will involve a series of roadshows around the shortlisted sites.
Ms Flint said: "The process is open, transparent and inclusive and we are testing every detail of the proposals with local authorities, stakeholders and local communities themselves.
"Within the lively debate about eco-towns and housing growth more generally, I do want to ensure that all voices can be heard."