Campaign to Protect Rural England said threats included proposals for over 80,000 new homes, new roads, opencast mines, new golf courses and industrial parks, the combined size of which amounts to a new town bigger than Slough within 20 years.
The call for tougher protection comes two years after the coalition’s pledge to protect green belt, said CPRE, citing communities secretary Eric Pickles who said in 2010 he would abolish regional planning so local people could better protect green belts.
Senior planning officer Paul Miner said planning inspectors were putting pressure on councils to allow building on the green belt to meet new national planning policies on land to be used for building homes.
"In times of economic slowdown, politicians can sometimes be tempted by the false promise of an easy construction boom," he said. "But destroying the countryside is not the path to lasting economic prosperity.
"Sustainable economic improvement can only come from the urban regeneration that has already done much to rejuvenate many largest cities. Building on the green belt is often justified by claiming there is a shortage of other land such as brownfield land.
"However, Government figures show the amount of brownfield land becoming available for re-development is far outstripping the rate at which it is being used and there is enough available for 1.5 million new homes."
He called on the coalition to ensure "smart growth", focusing investment and development within existing urban areas, rather than allowing the unnecessary loss of Green Belt land.
The map shows areas of risk including Cambridge, which is in consultation for up to 13,250 homes, Broxtowe which is looking at opencast mining and Nottinghamshire, which has gained permission to widen the A453.
England’s Green Belts covers over 1.6m ha, a total of 12.4 per cent of England’s total landscape and include 89,000 ha of sites of special scientific interest and 220,000 ha of broadleaf and mixed woodland.
A CPRE briefing is available from www.cpre.org.uk/resources/housing-and-planning/planning/item/download/2176