Derbyshire police targeted pubs in the run up to the busiest period for licensed premises and tested toilets for traces of cocaine.
A Buxton publican, who wishes to remain anonymous, has seen his pub fail a drugs test twice in two years and believes the results could be misleading.
"I believe that the police are trying to build a case against license premises to justify a late night levy and possibly to reduce operational hours,” he said.
But a spokesperson from Derbyshire police defended the move, telling the Publican's Morning Advertiser: “Carrying out these tests in pubs allows us to work with licensees to reduce drug use on their premises.”
Police claim the cocaine test they use, called DrugID, is “one of the most accurate” available and has no possibility for cross contamination with other substances.
But analysis by Selden Research - prompted by the licensee - has shown that some test results are ambiguous.
Terry Holland from the cleaning chemical development company used a standard cocaine test, Scott test (Cobalt reaction) wipes, on cleaning products commonly used in pubs, which gave positive results for cocaine. Holland concluded this test is highly sensitive so “could easily be affected by a chemical that has just been sprayed and wiped rather than rinsed”.
He added that it is currently not clear whether test results from DrugID can be contaminated by common cleaning and hygiene products.