One in 10 of licensed premises checked in Oxford failed a covert underage drinks operation.

More than 30 pubs, bars and off-licences across Oxfordshire were visited up to five times by 14 and 15-year-old police volunteers as part of the campaign.

No business failed the checks three times, which would have led to prosecutions, but One Stop, Simply Drinks and Que Pasa in Banbury and Co-op supermarkets in Eynsham each failed twice, said Thames Valley Police.

Visits in Oxford produced a 10.5 per cent failure rate, while in the north of the Cherwell district it was 34.8 per cent, in West Oxfordshire 15 per cent, in the Vale of White Horse 10.5 per cent and in South Oxfordshire 5.9 per cent. No premises visited in the south of the Cherwell district failed the test.

Overall, Oxfordshire recorded a 14.3 per cent failure rate.

Oxfordshire's police commander, Chief Supt Shaun Morely, said: "I'm disappointed with the licensed premises that failed, especially those from large chains.

"But I have been encouraged by how few premises failed. We also had particular areas where the results were excellent and others where there is a definite concern.

"Now we have highlighted those areas, licensing authorities can react in a targeted way and work with licensees to address their issues."

The scheme is part of a year-long police campaign highlighting the dangers of binge drinking and underage drinking.

Across the county, 18 pubs and off-licences passed the inspections without recording any failures.