Gordon Brown has promised to double the number of "eco-towns" to be built across the UK from five to 10.
Eco-towns will help ministers meet housing targets, Mr Brown said
The prime minister told the Labour conference in Bournemouth that a positive response to the project had encouraged him to expand it.
This showed "imagination", he said, adding that eco-towns would help the government meet housebuilding targets.
In May, Mr Brown promised communities of up to 100,000 low-carbon and carbon-neutral homes would be built.
Mr Brown told the Labour conference: "For the first time in nearly half a century we will show the imagination to build new towns - eco-towns with low and zero-carbon homes.
"And today, because of the responses we have received, we are announcing that instead of just five new eco-towns we will now aim for ten - building thousands of new homes in every region of the country."
This would help boost housebuilding to 240,000 homes a year, he said.
The eco-town idea was the first major policy announcement made by Mr Brown as he began his campaign to succeed Tony Blair as prime minister earlier this year.
Constructed on old industrial sites, they will be powered by locally generated energy from sustainable sources.
The government said that, with a month to go until the deadline, there had been about 30 expressions of interest in building eco-towns from councils, developers and others.