The West Midlands green belt is "under attack as never before" from creeping developments, according to conservationists.
The Campaign to Protect Rural England today launches a national push aimed at reinforcing green spaces and restricting urban sprawl.
Developments like the M6 Toll, potential expansion at Birmingham and Coventry Airports, the proposed privately built M6 Expressway or M6 widening schemes through Staffordshire, the planned Brownhills bypass and major expansion on the Blythe Valley Business Park near Solihull are all highlighted as ways in which the green belt has been eroded or is under further threat.
Britain celebrates 50 years of the green belt planning protection and CPRE believes it remains one of the "sharpest tools in the planning toolkit".
But it warns that the effectiveness of the policy is being blunted by the "top-down imposition" of boundary reviews which erode public confidence and fuel land speculation, with damaging consequences for the countryside.
Gerald Kells, West Midlands CPRE policy officer said: "Although the Government should be the staunchest, most reliable ally of green belt, it continues to implement policies and support proposals in this region and elsewhere which undermine green belts across the region.
"The M6 Toll has recently cut a huge swathe through our green belt and development pressure attached to the road is a major threat."
He added: "But plans for an M6 Expressway and the expansion of Birmingham Airport in response to the Aviation White Paper show that major incursions can still gain support from Government.
"And although some local councils are opposing plans which eat into the green belt - for example plans for industrial sites at Peddimore and Bassetts Pole were recently withdrawn by Birmingham City Council - others are eating away at the green belt.
"The Brownhills Bypass and plans for a hotel at Chasewater Heath are perfect examples as are plans to extend the Blythe Valley Business Park close to Solihull."
Mr Kells added that the CPRE campaign was urging the Government and local authorities to "pull back from the brink of green belt destruction in the West Midlands" and provide the leadership to ensure green spaces are protected into the 21st Century.
The chief purpose of the green belt is to protect the countryside from urban sprawl and prevent towns and cities merging. England has 14 separate green belts covering about 13 per cent of the nation.
CPRE chief executive Shaun Spiers said: "Of all planning policies, green belt is probably the best loved by the public and it's the envy of other countries. For millions of people living in our largest towns and cities, they are the countryside next door."