A Grade II listed building is at risk of falling down after the local council opposed plans to restore it, the owner says.
Hanworth Park House in west London has stood empty for 25 years.
But Hounslow Council said plans to build new homes on the green belt site, to raise the £10m restoration costs, are unacceptable.
Owner Gary Cottle, 51, said he will be submitting a new planning application soon.
First used as a hunting lodge by King Henry VII, Hanworth Park House acted as a military hospital in World War I and was most recently a nursing home.
It burned down in 1798 and the new build has been standing since 1802.
Mr Cottle, who bought the house three years ago, wants to build new homes in a section of Hanworth Park in order to raise restoration funds.