Firms believe government has underestimated amount of used land available for new homes.
Housebuilders have expressed scepticism at the results of the government's first national database of brownfield sites.

The figures, unveiled last Thursday, showed that there are enough sites for only 710 000 dwellings, and indicated particular shortages in London and the South-east, where demand is most acute.

But several housebuilders doubted whether the figures were accurate. Tony Carey, managing director of Berkeley Group South-east subsidiary St George, said: "They can't have looked properly in the South-east.

"There are tranches of brownfield land that need development in areas like Redbridge, Tower Hamlets and Newham. Just look at the number of housing estates in south London that need to be redeveloped." Carey said he believed London's housing need could be satisfied almost entirely through the development of derelict land in the capital.

He said many developers were put off by the demands local authorities made in terms of building facilities, as part of the trade-off to get planning approval.

Carey said: "There's more brownfield land if people would think differently. Local authorities talk about planning gain, but in some locations redevelopment itself is a planning gain." Redrow Group managing director Paul Pedley echoed Carey's view. He said: "It's all very well identifying land through the database, but they've got to get the land to [planning] consent more quickly.

We need to remove the delays from the planning system." Dr Ian Roxborough, planning director at Wimpey, which builds about 13 000 homes a year, said: "I'm surprised the new national database could so readily identify land that was apparently suited to residential development.

"This means either the survey, which took less than a year to produce, is unlikely to be dependable, or if it is, then for a local authority to take five years to produce just one local plan is even more outrageously inefficient than we already believe to be the case."

The database was set up as part of the government's policy to ensure that 60% of the 3.8 million homes it predicts will be required in the UK to 2021 are built on previously developed sites. A DETR spokesman said criticism of the database was unfounded. He said: "It's preliminary data and there's a lot more that has to be worked into it. The 3.8 million figure goes up to 2021. The database represents what we have now; it's only part of the picture."