Tighter quotas to create more "affordable homes" are likely to backfire, Winchester City Council has heard.

Housing consultants, Adams Integra, published the findings in a report requested by the authority.

Conservatives have attacked the ruling Liberal-Democrat group over their proposed quotas. Council leader, Sheila Campbell, has accused the Tories of siding with developers at the expense of residents.

The Lib-Dems want to increase the number of affordable homes developers are required to build in the Winchester district. Such properties are often sold to "key workers" such as nurses and teachers.

At present, at least 30% of homes must be affordable in schemes of 15 dwellings or more in towns and five or more in villages.

The Lib-Dems want to drop the threshold to five properties in towns and two in villages. They also propose 40% of properties should be affordable in Winchester, and 35% elsewhere in the district, compared to 30% at present.

To establish if the new figures were practical, the Lib-Dems commissioned the Adams Integra report.

An executive summary of their findings was circulated to council members and posted on the authority's website.

The summary said: "Winchester City Council's proposed affordable housing policies will have a negative impact on housing site viability, and therefore on site supply in general."

The report added that Winchester town was the only part of the district that would remain attractive to developers.

Tory group leader, Barry Lipscomb, branded the report as a "spectacular own-goal" for the Lib-Dems. He also argued that they had "buried" the report on a part of the council website that was difficult to find.

"Unlike the Lib-Dems, we will work with parish councils and builders to ensure the scale and nature of development is right for both, and not just lay down inflexible targets."

Mrs Campbell admitted her party was rethinking some of its proposals. She said that the Adams Integra report had been commissioned to ensure they made the right choice.

"The Tories have shown their true colours by coming down on the side of protecting the profits of developers rather than trying to get subsidised housing for hard-pressed residents.

"The Lib-Dems are on the side of those ordinary people doing ordinary jobs for ordinary pay, but who cannot find homes to buy because the prices are extra-ordinary."

* The Adams Integra report summary may be viewed at http://www.winchester.gov.uk/planning/local_plan/inquiry/Adams%20Integra%20Exec%20Summary.pdf