Birmingham has 18,000 unoccupied properties - the highest number in the country and the equivalent of a small town.

The majority of the empty properties, from the city's stock of 400,000 public and private-sector dwellings, belong to private investors.

And with 23,794 people on the housing waiting-list - 940 of them classified as homeless - the city council has warned it is to step up the enforcement of compulsory-purchase orders on long-term unoccupied properties in a bid to tackle the shortages.

According to a MORI survey, five per cent of privately-owned residential properties in Birmingham is currently unoccupied - 1.7 per cent higher than the national average. Of the 17,800 total lying empty in the city, 15,000 are privately owned with the rest owned by the city council and housing associations.

Although the proportion is not the biggest in the country, it is the highest number of any authority.

Birmingham City Council, which commissioned the research, has created an Empty Homes unit to look at ways of bringing the accommodation back into use. The MORI poll suggests people investing in property in this way are not that bothered about gaining an immediate return and instead are happy to sit on their capital and let it grow for several years.

Councillor John Lines (Con Bartley Green), cabinet member for housing, said: "The market research undertaken by MORI has improved our understanding of the complex issues around empty properties and the results will enable us to develop and deliver a programme of strategic and targeted interventions aimed at bringing empty homes back into use."

The authority is looking at enforcing new laws that will come into force in the autumn allowing it to take action over accommodation that has been unoccupied for seven years. Enforced sales may also be issued on property owners who have incurred council debts, for example nonpayment of council tax.