A call for tighter drink drive laws was made last night after police collared three drivers a day who were over the limit during a summer crackdown.

One out of every 10 drivers tested by police in Oxfordshire during June were arrested for failing the breath test, or refusing to provide a sample.

Now the force's top road police officer and the family of a teenage boy killed by a drink driver have called for the alcohol threshold to be cut.

Last night Supt Mick Doyle, head of roads policing in Thames Valley, also suggested proposals by the Government's chief medical officer Sir Liam Donaldson to set a zero alcohol limit for drivers aged between 17 and 20 would be unworkable.

Instead Supt Doyle has called for the alcohol limit to be lowered - from 80mg in 100ml of blood to 50mg - in a bid to encourage more people to stop drinking and driving.

He said: "It is almost impossible to impose a no alcohol limit on young drivers. Alcohol can remain in the system for a long time, so we could end up with people failing for having a tiny bit of alcohol in their blood.

"My personal view is the limit should be reduced and not just for young people. If we brought the limit down it would make more people realise they should not be drinking anything then driving.

"The idea of 50mg is effectively telling people don't drink and drive. The problem of having a zero alcohol limit is the body retains a small amount of alcohol if they have had a drink.

"We would end up failing people with three or four mg of alcohol which doesn't have any effect on ability to drive.

"It is not operationally practical. There should be zero tolerance, but a zero alcohol limit isn't practical."

During the summer crackdown, officers breath-tested 1,117 drivers across the county.

They arrested 62 motorists who were over the limit and 32 drivers who failed to provide a specimen of breath - a rate of about nine per cent.

The number of drink drivers caught this summer had fallen from 14 per cent during a similar operation last Christmas and 15 per cent in June 2007.

Jane Evason, from Grove, lost her 19-year-old son Gareth when he was killed by a drink driver 10 years ago. She also believes the limit should be reduced, but thinks a zero limit would be unworkable.

She added: "Lowering the limit would work because it would make people stop and think. We need to educate drivers, especially the younger ones, that they risk theirs and others' lives when they drink and drive."

The Department of Transport has now paid for breath test kits in every patrol car in Oxfordshire and the Thames Valley.