Plain packaging could cost convenience retailers nearly £40m a year, according to a ground-breaking experiment carried out in four English stores.

Commissioned by the Rural Shops Alliance (RSA) and carried out by research agency Visuality, the study saw transaction times double as confused staff struggled to locate products and made mistakes, resulting in frustrated shoppers and lost sales.

Based on these figures the RSA estimates that plain packaging could scrape £37m a year off retailers’ bottom lines.

As part of the study, each store was fitted with special CCTV cameras, enabling customer and staff behaviour at the cigarette display to be monitored.

At more than 3,000 sq ft in size, two of the convenience stores tested were already complying with the tobacco display ban legislation while the plain packaging trial was carried out.

More than 4,000 tobacco transactions were carried out across the four stores during the test period, with all reporting significantly higher selection and transaction times, while error rates increased by up to six times.

Customer surveys carried out after sales also revealed that, on average, 14% had found it “more difficult to find the brand they asked for.”

The two large convenience stores already complying with the display ban encountered even greater problems, with 46% of shoppers questioned at the Mount Sorrel test store in Leicestershire saying the process had been difficult. The high number of part-time staff employed at this store made it harder for staff to adapt to the changes and learn the planogram.

The Association of Convenience Stores (ACS) has urged the Department of Health to consider the study’s findings. Chief executive James Lowman said: “This study clearly shows that retailers will suffer if standardised packaging for tobacco products is introduced.

“Ministers should wait and carefully assess the impact of standardised packaging when it is imposed in Australia later this year. This is the only way to have reliable data on the scale of the business impact. Failure to do anything else would be irresponsible.”