Drinks retailers in Lincolnshire performed well during tests on Aug 9, with only three
of 18 shops tested in Louth, Mablethorpe and Alford selling alcohol to under-age customers.
PC Pete McLeod, of Louth Neighbourhood Policing Team, said it was one of the most successful test purchasing operations the area had seen but
there was "still room for improvement".
In Buckinghamshire, six of the 21 tests in on and off-licensed premises made between March and June of this year resulted in illegal sales.
John Fox, of Thames Valley Police, said: "That figure highlights the improvements made in the industry in recent years as a result of the ongoing efforts of all involved."
Areas that did not perform so well included Gloucestershire, where four of 12 shops tested sold alcohol to two 15-year-old test purchasers on Aug 9.
In Somerset, the licensing authority said it was considering revoking licences at some shops after 15 of the 38 off-licences checked over a four-month period failed tests.
Milton Keynes licensing officer Lynn Poizat also warned that three off-licences in the area would have their licences reviewed after 60 test purchases resulted in nine illegal sales.
Of 145 test purchases made in Berkshire, 33 resulted in illegal sales and in Oxfordshire the failure rate was 16 out of 112.
Official Home Office figures are not due to be published until September, but sources have revealed an off-trade failure rate of 14 per cent compared with 20 per cent in the on-trade (OLN, Aug 10).