Protected green belt land should be built on with local communities given the power to decide what land should be sacrified to make way for houses, according to a leading Conservative think-tank.

But the call has been given short shrift by the Kent branch of the Council for the Protection of Rural England (CPRE), which described it as "nonsense on stilts".

Dr Oliver Hartwich, an economist with Policy Exchange, says the Government must tackle the myth that there is a shortage of land.

He argued that with more than half of land England afforded protection from development, it was already difficult to build the homes the country "desperately needed".

In an article, he writes: "The 'green belt' description has elevated imagination over reality in Britain's planning system.

"To the public, the areas it refers to seem to be much-needed reserves of nature in an over-crowded, concrete Britain. They are believed to be the last remnants of what was once England's green and pleasant land."

In fact, much green belt was industrialised agricultural land, rather than land "full of birds, bugs and gentle hedgerows".

As a result, there should be a "more open discussion about which areas should be developed and how...it should not be conducted as either for or against the green belt".

Dr Hilary Newport, director of Kent CPRE, said that safeguarding green belt land was even more important in the face of the Government's huge house-building programme for the south east.

"This is nonsense on stilts, written by an economist without an ounce of commonsense. It's true that some green belt is unloved and damaged - but that is not a reason for it to be developed on. There is already scope in existing legislation for building on green belt land."