Housing minister Grant Shapps said that government plans to release formerly-used public land would provide capacity to build up to 100,000 new homes by 2015.
Half of these could be built on land owned by the first four departments to publish their strategies: Ministry of Defence, Department of Health, Department for Transport, and Department for the Environment, Food & Rural Affairs.
Property specialists are working with each department to challenge them to release as much land as they can for new homes.
Mr Shapps said: "The government is one of the country's biggest landlords, so at a time when we desperately need more homes, we have a critical role in making new sites available for developers and communities.
"So I'm delighted that government departments have quickly taken up the ambitious challenge to release land with capacity for over 50,000 new homes, and that property specialists will continue to work with these departments to make sure that no stone is left unturned. I will look to ensure that as much of this public land as possible is available under our innovative Build Now, Pay Later model - helping get developers on site and laying the foundations for these homes as quickly as possible.