Calls for 20mph limits in Oxford's residential roads have been renewed after an Oxford Mail investigation found nearly half of motorists speeding in the city.

Pedestrian groups and Oxford Green Party said the spotcheck showed 30mph roads needed to be made into 20mph zones.

Those calling for the change said although drivers might continue to speed, cutting the limit to was likely to reduce speeds overall.

As reported in Saturday's Oxford Mail, crime reporter Jo Duckles clocked 224 47 per cent of 476 drivers exceeding speed limits during 30-minute periods at four different locations in the city.

In Bayswater Road, Barton, the speed camera caught one motorist driving at 57mph in a 30mph zone.

Campaigners who took part in a rally in Oxford last November as part of a national 20 Is Plenty campaign said the findings supported their views that action was needed to curb speeds.

Mother-of-two Jenny Evermore was among residents in Rose Hill who asked for traffic-calming measures and a 20mph speed limit in the estate's Church Hill Road, Westbury Crescent, Kelburne Road, Mayfair Road and Beauchamp Lane last year.

She said: "I do still believe that 20mph limits are needed on many Oxford streets.

"Drivers who speed might not change, but most people will go about 10mph over the speed limit so if it's reduced to 20mph then that's going to make people slow down overall."

City Council Green group leader Craig Simmons said the party was renewing calls for the extension of existing 20mph zones in the city in light of the Oxford Mail's survey.

The party's city and county councillors have jointly emailed David Robertson, the county council's cabinet member for transport, requesting the extension.

Mr Simmons, an East Oxford city and county councillor, said: "The email highlights the inconsistency of the current situation, where some main roads, such as Cowley Road, are 20mph, whereas the neighbouring residential streets are still 30mph. What we have now is a pig's ear of a scheme, which confuses drivers and does residents no favours."

Some residents have had success in campaigns for 20mph zones. In 2003, people power resulted in lower limits being introduced in parts of north Oxford, including Kingston Road.