Local authorities willing to allocate green belt land for development, research shows

The survey, which was carried out by the Local Government Information Unit, found that 51% of 59 participating councils said they were now "likely or very likely" to allocate green belt land for development.

More than half of the overall 147 participating councils, including those with no green belt land in their area, said that they had brownfield sites available which were not considered viable for development.

"The green belt has been the star feature of British town and country planning for half a century," said National Trust chairman Simon Jenkins in a statement. "In one of Europe’s most congested countries, it has prevented urban sprawl, protected a vision of rural England and retained access to green spaces for urban dwellers that has been admired worldwide."

Jenkins said that the planning system as a whole should "attach a greater weight to protecting green spaces". "The Government’s definition of ‘sustainable’ is in practice being interpreted as ‘profitable’, and has effectively killed the former planning presumption in favour of brownfield land. What is now happening is a policy of let rip, leading to steady erosion. For the first time in British planning history, planning control is now the slave not the master of profit," he said.

The National Trust said that new National Planning Policy Guidance due to be published by the Government in early 2014 could increase the threat to green spaces by causing local authorities to release more land than is necessary for development in the countryside, including in the green belt.

It called on the Government to amend the guidance to "ensure the planning system delivers on the Government’s promise to deliver a ‘brownfield first’ policy, and to reaffirm its commitment to protect valued green spaces from development".