THE model for Scotland’s planned flat-rate deposit return scheme for drinks cans and bottles could “severely hamper” efforts to tackle childhood obesity, public health experts have said.

Setting a fixed rate of 20p for all containers, regardless of their size, could encourage more people to buy larger bottles of sugary drinks, they claimed.

The group, which includes senior figures from Glasgow and Strathclyde universities, as well as the London School of Economics, argued there should be a graduated charge, rising in line with the size of the drink container.

However, the boss of Scottish environment charity which has campaigned for a deposit return scheme since 2015, said the call “seems to be based on a misunderstanding of how deposit return works”.

Scotland is the first part of the UK to have announced plans to bring in a deposit return scheme in a bid to boost recycling.

Under proposals to be brought in before the end of the current parliament, a 20p charge will be levied on the vast majority of drinks containers, including PET plastic bottles – used for fizzy drinks and water bottles – glass bottles and steel/ aluminium drinks cans.

However, in a letter to The Herald, they said: “For smaller servings of less than half a litre a 20p deposit represents a huge percentage increase on the price charged to the consumer. For larger containers the increase is less significant.

“A flat deposit fee thus risks incentivising consumers to purchase larger containers of sugary drinks. This could severely hamper the Scottish Government’s efforts to meet its targets on childhood obesity.”

John Mayhew, director of the Association for the Protection of Rural Scotland, suggested the group may have misunderstood how the scheme will work. He said: “A deposit does not add to the cost of a drink – it is fully refunded when you take an empty can or bottle back.

“What’s more, some deposit return systems internationally use a flat deposit rate and others use different levels for containers of different sizes.

“No evidence has been presented that suggests either approach has any impact on obesity.”

A Scottish Government spokesman said: “Tackling obesity is a priority for the Scottish Government and last year we published a comprehensive plan which sets out a wide range of actions to support people to eat well and have a healthy weight.

“We were the first part of the UK to commit to a deposit return scheme which is ambitious in scale and scope and gives the people of Scotland a clear and straightforward way to do their bit for the environment.”