Three pubs, a shop and a social club all served alcohol to children in the latest round of police test purchasing operations.
Police sent children aged 15 and 16 into eight licensed premises to buy drinks and only three refused and asked for identification.
Staff were fined £80 at The Penny Black, in Sheep Street, and The Star Inn, in Bucknell Road, both in Bicester, and the Blacks Head public house, in Bletchingdon.
Kidlington Green Social Club, in Green Road, and the Co-op store, in Banbury Road, Kidlington, also failed and were fined £80, following the operation last month.
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