Prospective eco-town developers have been told they must notify relevant councils about their proposals if they want to win a place on one of the government’s 10 preferred sites.

Communities department officials wrote to all developers behind eco-town bids at the beginning of this month, telling them to send their bids in full to councils in which the towns would be built, an internal source said.

The news follows the department’s announcement before Christmas that it would consult a longlist of councils about proposals in private before ministers decide on a public shortlist of 10 in February. The source said: “It was felt important to ensure councils and the department were working with the same information when discussing proposals.”

Countryside campaigners have complained about a lack of transparency in the selection process for the eco-towns, announced by prime minister Gordon Brown in September.

The news comes as housebuilder Persimmon admitted it was discussing eco-towns with the government. Mike Killoran, group finance director, said: “We are talking to the relevant parties about particular opportunities.”

Persimmon has a landbank of up to 30,000 plots for homes without planning permission. One of the criteria for eco-town proposals was that they were for sites not currently identified in the planning process.

The admission follows rumours Persimmon had made a large number of eco-town bids.