50 years on, England's Green Belts are under attack as never before and the biggest threat is from government itself, rural campaigners reveal in a report published today.

Shaun Spiers, Chief Executive of the Campaign to Protect Rural England, said ministers have repeatedly affirmed their commitment to Green Belts and the government should be their staunchest most reliable ally.

However, said Mr Spiers, the greatest source of pressure on Green Belt land is government policy. "A pattern is emerging of sustained attacks on Green Belts across the country," he said.

"From the government's Sustainable Communities Plan to the Aviation White Paper, a major onslaught on Green Belt is underway unlike any seen since national Green Belt policy was introduced 50 years ago," said Mr Spiers. "And many local councils - the first line of defence against Green Belt incursion - are meekly following the government's lead."

Mr Spiers added: "A crucial element of Green Belts is the permanence of their boundaries. Green Belt policy is one of the sharpest tools in the planning toolkit. But its effectiveness is being blunted by the top-down imposition of boundary reviews and careless talk of 'replacing' lost Green Belt land elsewhere."

"The Green Belts' chief purposes are protecting the countryside from urban sprawl and preventing towns and cities merging."

"Of all planning policies, Green Belt is probably the best known, and best loved by the general public — and it's the envy of other countries. It has been remarkably successful in stopping sprawl and protecting the countryside around our towns and cities, thereby improving the quality of life of us all."

"'If the Green Belts didn't exist, we'd have to invent them. For millions of people living in our largest towns and cities they are the countryside next door. We want everyone to enjoy and appreciate them, and for them to be better looked after."