It comes after Ms Reeves used her first speech as Chancellor to announce “urgent steps” to deliver the Government’s central mission to “kickstart economic growth”, including reintroducing mandatory local authority housing targets and reviewing green belt land.

Deputy Prime Minister Angela Rayner will write to local planning authorities to tell them to start reviewing green belt boundaries to prioritise former industrial brownfield sites and so-called grey belt land for development to meet housing targets.

Green belt land is land surrounding 16 city areas across England that is protected from development. It spans roughly an eighth of England’s land area, according to JLL property consultants, with much of it in the prime commuter belt territory around London that has traditionally been the Tory heartlands. 

It was a Labour manifesto pledge to release grey belt sites within it, such as disused car parks, for housing development. 

Knight Frank has identified 11,000 sites that could be potentially designated as grey belt, which between them have the potential to deliver 200,000 new family homes.

Developers and landowners are now assessing what new opportunities there will be for them to build.

Mr Stoddart said: “They’re saying ‘we have got a lot of sites that could be classified as grey belt that are well located near train stations’. There is a fresh emphasis to actually get on with this.”

Those interested include a leisure company which owns “massive” sites in the green belt. “It has been looking to find other ways to get a capital return from them. Suddenly, if they are classified as grey belt, there is an opportunity to build their businesses and diversify,” Mr Stoddart said.