The introduction of plain cigarette packaging led to an increase in the sale price of leading brands, new research suggests.

A study by Stirling University found that the price of top-selling cigarettes increased by almost 5% – or an extra 38p on a pack of 20 – in the 18 months after the legislation was introduced. The price of hand-rolling tobacco also rose by about 8%, or 91p on a 30g pack.

Researchers said their findings were at odds with tobacco companies’ predictions that plain packaging, which became mandatory in May last year, would lead to lower prices and greater affordability.

Dr Nathan Critchlow, of Stirling’s institute for social marketing, said: “Tobacco companies were strongly opposed to plain packaging. They appeared adamant that, if the policy was implemented, brands would only be able to compete on price, which would result in lower prices, greater affordability and, consequently, increased consumption.

“Our study, however, provides early evidence that these concerns of lower prices appear to be unfounded. We found that, as well as the sale prices, recommended retail prices also increased. This suggests that tobacco companies instigated the price rises – and that their predictions of falling prices and rising affordability were intended to deter the government from implementing the policy.”

The team analysed electronic point of sale data from 500 small retailers in Scotland, England and Wales over the 12-month transition period and then for six months after the legislation became mandatory.

The average price per cigarette and price per gramme – both adjusted for inflation – were examined for 20 of the leading fully branded tobacco products and their standardised equivalents.

The study was funded by the Cancer Policy Research Centre at Cancer Research UK, and was published in the international journal Addiction.

Kruti Shrotri of Cancer Research UK said: “Plain packaging for cigarettes is an effective public health measure to reduce the attractiveness of tobacco to young people. The tobacco industry were clearly saying anything they could to try and undermine this health measure and protect their profits.”