An independent assessment of a possible eco-town project has concluded that the proposal is not financially viable.
The work for local authorities affected by plans to build at Middle Quinton near Stratford-upon-Avon suggested the scheme would have a deficit of £373m.
Following the report, the six councils warned the eco-town could not proceed without "massive public subsidy" which would be better spent elsewhere.
The councils are from Warwickshire, Worcestershire and Gloucestershire.
According to consultants CB Richard Ellis (CBRE) the money to be made from the development would not be sufficient to fund the provision of infrastructure such as public transport, roads and schools.
The councils' eco-town joint working group chairman Charles Gillams said: "The independent assessment confirms our long held doubts about the viability of an eco-town in this location."
Eco-towns, intended to tackle the twin problems of housing shortages and climate change, have to be carbon zero as a whole, be an "exemplar" in one area of environmental development and have at least 30% affordable housing.
Up to 10 are proposed, with five being built by 2016 and a further five by 2020.
The Middle Quinton development has been strongly opposed by local residents.
Last month campaigners against the scheme lost a High Court case when a judge rejected their complaint that there had been a failure to consult the public properly over the "eco-towns" policy.
But they vowed to go on fighting the proposals to build 6,000 new homes near Long Marston, Warwickshire, 10 miles south of Stratford-upon-Avon.
The independent assessment published on Tuesday was commissioned by Cotswold District Council, Stratford-on-Avon District Council, Wychavon District Council, Gloucestershire County Council, Warwickshire County Council and Worcestershire County Council.