"Park and ride" schemes are shifting traffic and related pollution problems from urban areas into the countryside, rural campaigners have warned.
The CPRE says park and ride has created 50,000 parking spaces
The Campaign to Protect Rural England (CPRE) estimates 40 towns and cities in England operate park and ride schemes.
The schemes encourage people to leave their cars on the outskirts of centres.
A CPRE spokesman said: "Increasingly large areas of countryside are being buried under tarmac in the name of sustainable transport."
The CPRE is releasing the findings of a survey into park and ride schemes at a conference on Thursday.
Comments to be made by Paul Hamblin, CPRE's head of transport policy, were released ahead of the conference.
He said park-and-ride posed a "leading threat" to Green Belts.
"If this continues, every major town in England will have a necklace of car parks around it and it won't be a pretty sight," he said.
"We need to reduce traffic levels overall and improve public transport closer to where people live to provide genuine transport choices."
Spokeswoman Anne Robinson from the CPRE told BBC Radio Four's Today programme the schemes were "trashing" the countryside.
"Park and ride results in large green field sites, if not greenbelt, being covered in tarmac and then you get the intrusion of the traffic," she said.
A spokesman from the Department of Transport said it was up to local authorities to decide how to handle any traffic issues in their areas.
"Park and ride schemes can have real benefits in tackling congestion at local levels, but it's for local authorities to decide what solutions are best for them."
He said authorities also had to consider the environmental impact of any schemes they might adopt.
David Evans, leader of the city council in Chester - where there are four park and ride schemes - said that in 20 years the schemes had not led to "other forms of urbanisation in the countryside".
"We have over a million people a year using these park and ride sites who would otherwise be driving their cars into the city centre."