Where does the government want to build 1.5 million new homes?

Previously developed land will be prioritised for new homes, the government said. These “brownfield sites” can include places like derelict industrial or commercial developments.

However, Pennycook said brownfield land alone will not be enough to deliver the number of homes the country needs.

As a result, councils will also be ordered to review green belt boundaries – which were created to prevent urban sprawl – by identifying lower quality “grey belt” land that can be built on.

The government has previously described the grey belt as “poor quality and ugly areas” on the green belt. A disused garage in Tottenham, north London, which could not be built on because it was within the green belt, has been used as an example.

There is no official data on the size of the grey belt.

However, estate agent Knight Frank carried out research and identified 11,000 previously developed sites – making up less than 1% of the green belt.

These were concentrated in the south of England, with just over 40% within the London green belt area.

They estimated that 100,000-200,000 new family homes could be built on grey belt sites.

The prime minister said development would be locally led, with the land developed “brownfield first, grey site next, and greenbelt last”.

Conservative shadow housing secretary Kevin Hollinrake said: “This planning framework pushes development to rural areas, concreting over green belt, green fields and over our green and pleasant land.”