Petrol stations were the least likely retail category to ask for proof of age in a test purchasing operation for alcohol and tobacco.

Retailers sold alcohol to nearly one in six teenage mystery shoppers in 2016 without asking for proof of age, according to new data from retail age check auditors Serve Legal.

The company’s retail testers, all of whom are young-looking 18 and 19 year olds, undertook nearly 43,000 (42,984) alcohol sale tests in supermarkets, convenience stores and petrol stations across the UK in 2016. Age ID was requested in 83% of visits before alcohol was handed over.

Petrol stations were the lowest-performing retailers, passing 78% of alcohol age check tests. Pass rates and testing levels fell for the second year running.

Supermarkets were the highest-performing retailers, passing 84% of tests in 2016 compared with 87% in 2015. Test levels increased by 1% in the last year (21,069 in 2016 versus 20,704 in 2015) and by 32% in the last five years (14,224 in 2011).

Scotland maintained its historical position of achieving the highest overall alcohol test pass rate in the UK with retailers there passing 87% of age check tests in 2016. Northern Ireland was the poorest performer with a pass rate of 72%.

Tobacco products, including e-cigarettes and vaping products, were also sold to one in four Serve Legal mystery shoppers in 2016, with age ID requested in 76% of visits. Pass rates for all retailers improved by one percentage point compared to 2015 and test levels were nearly 3% higher (3,982 in 2016 versus 3,877 in 2015). Supermarkets reported the highest pass rates in 2016, passing 82% of tests while petrol stations performed worst, passing 67% of tests.

Proof of ID for was more likely to be requested for sales of traditional cigarettes than e-cigarettes, with retailers passing 77% of age check tests for traditional cigarettes compared to 72% for e-cigarettes. In 7% of tobacco sale visits by mystery shoppers, products were retrieved from the cabinet before ID was requested. Retailers in south central England achieved the UK’s highest tobacco sale test pass rate in 2016, passing 82% of age check tests. The poorest performer was Northern Ireland where retailers passed just 71% of tests.

Ed Heaver said: “Rigorous, regular testing for age-restricted sales sees compliance levels improve dramatically which reduces the risk of alcohol, tobacco and other harmful products getting into the hands of children. It should be an integral part of retail training and operational best practice, not a panic purchase after a sting by trading standards or the police.”