A shortage of affordable housing could drive more than 500 families out of North Wiltshire, a new survey has discovered.

North Wiltshire District Council commissioned the survey by David Couttie Associates to check out the need for new homes.

More than 2,000 homes have concealed households within them people who should be living in their own home but can not afford to do so.

Although the majority are single adults living with parents, 790 households have couples or people with children forced to share a home.

The survey discovered 64 per cent of concealed households did not have a large enough income to buy a terraced home.

The cheapest homes in the district are flats, costing an average of £54,921 and terraced houses, at £78,355.

More than a third of concealed households have low annual combined incomes of below £15,000, and nearly two thirds had combined incomes below £20,000, which is needed for first time buyers to get into the housing market.

"We estimate that a new purchaser would need an annual income of around £17,500 to buy a flat, the cheapest property available, and at least £20,000 to buy a terraced house, which are in reasonable supply," the report said.

The survey found of the 4,455 households planning to leave the district in the next five years 577 would be moving because they couldn't afford to buy a home.

The district could also face a crisis in affordable rented homes, with a shortage of more than 1,000 by April 2005.

The estimated 40 per cent increase in the number of elderly people aged 80-plus in the district between 1991 and 2011 will also put housing under strain.

Already 17 per cent of households have a member with a disability, mainly people who find walking difficult. Consequently the report concludes around an extra 1,600 units of sheltered housing will be needed.

The district council hopes the information will help it tackle housing problems in the Local Plan, and negotiate for affordable housing on new housing development sites.

The Englands site in Chippenham, for example, is currently under development and 20 per cent of the 160 new homes will be earmarked for social and low-cost housing.