More than 20,000 newly built private homes are unsold in the UK, senior industry figures have told the government.

Building has learned that industry leaders have also told ministers that work has started on a further 60,000-70,000 properties that are as yet without a buyer.

These figures are on top of the 9,000 empty shared-ownership homes on the books of registered social landlords, according to the Homes and Communities Agency. If true, the estimate of 20,000 empty homes means stock worth £4bn is unsold, based on an average UK house price.

It would also mean that a seventh of all the homes built in the past 12 months have not been sold. Sources said the figures were not based on an exact audit but were an approximation from the experiences of a wide range of housebuilders.

Stephen Stone, chief executive of Crest Nicholson, said it tallied with his experience. He said: “There’s a huge overlay at the moment, and that means builders are forced sellers and that the lack of activity is further driving down prices. The housebuilding industry is essentially on its knees.”