Concerns have been raised over moves to lower speed limits through Oxfordshire villages.

Police and leading motoring organisations have called on local councils to act sensibly when debating whether to lower limits.

The controversy stems from Oxfordshire County Council's four-year project to target speeding troublespots in rural areas.

Local people and councils are asked to identify areas of concern and suggest what the speed limit should be.

But Pc John Croxton, traffic management officer for Thames Valley Police, said speed limits on some roads had been changed despite police opposition.

A county council road safety worker also said many changes were approved because of pressure from parish councils.

Pc Croxton said: "Research has shown that if most drivers are choosing to travel at 50mph, and you reduce the limit to 30mph, people will only drop their speed by about three to four miles an hour.

"We police by consent and rely on the majority of people respecting what the police do.

"If you impose a speed limit that people do not see as realistic, you are not policing by consent."

Colin Carritt, area engineer for Oxfordshire County Council, agreed, but said parish councils often demanded tougher speed limits.

"The police have said they do not have the resources for extra speed limit enforcement, which is one of the reasons that speed limits have got to be seen as reasonable," he said.

Kevin Delaney, traffic and road safety manager for the RAC Foundation, said he backed speed restrictions through villages, but not on surrounding roads.

He added that the police were less likely to enforce speed limits they felt were excessive.