Ministers are ready to allow some redevelopment of green- belt land which is already occupied or developed but derelict or underused. The guidance, which will be published soon, would permit development on abandoned industrial sites, run-down light commercial property, old power stations and former garden centres.
The scope for redeveloping such sites and removing eyesores is limited under the existing guidance.
'We don't have to be pious about this,' said one ministerial source. 'There are areas of land, such as old pig farms, which are just falling to bits, which could be put to some productive use.'
The green belts, covering 6,000 square miles and 12 per cent of England, have been the prime defence against the sprawl of cities in the post- war years; the belt round London accounts for a third of that area. Developers, especially housebuilders, have long campaigned against them and several big city councils wish to see major inroads made into their green belts for the sake of local economic growth.
Ministers are keen to promote development which would create jobs without damaging the environment. Developers might be expected to screen buildings with new woodland and it is unlikely that permission would be given for big housing developments in green belts.
The planning guidance is being changed following lengthy consultation; a draft was issued in February. Ministers had been inclined to make more dramatic incursions into the protected areas but decided that would be politically unacceptable.
Any move to allow development in the green belt could prove highly controversial and electorally risky for the Conservatives. Many Tory MPs have seats in the Home Counties where the buffer zones are hotly defended.
Environment ministers say that they have begun a 'quiet revolution' in planning policy which will eventually affect many voters. A series of reviews led by David Curry, the minister with responsibility for local government, is intended to end the Eighties explosion in out-of-town shopping centres and other development which encourage the use of private cars at the expense of public transport, walking and bicycling.
The Council for the Protection of Rural England said that the Government's new guidance had to ensure that any new building on derelict green-belt sites preserved the open, rural character and greenery of the area.
Neil Sinden, planning campaigner for the council, said that while large, high-intensity development had to be ruled out, 'we're not against the idea of finding ways of improving derelict and abandoned sites in principle'.
The council is much more worried about another aspect of the new guidance - what it sees as a weakening of the presumption against inappropriate development in the green belt. It has obtained a legal opinion from a leading planning lawyer, Robert Carnworth QC, which says the new guidance undermines existing green-belt policy.