The sugar content of soft drinks has undergone a “striking” reduction since the introduction of a so-called sin tax, researchers have found.

Drinks manufacturers have cut the amount of sugar in their products since the levy of between 18p and 24p a litre was introduced in April 2018.

The Oxford University research, published in BMC Medicine, claims there has been a 29% reduction in the total amount of sugar sold in soft drinks in the UK between 2015 and 2018.

Researchers looked at the nutritional information on a range of soft drinks, including carbonated drinks, juice drinks and energy drinks, and combined their findings with sales data from 2015-2018.

The UK’s two biggest soft drinks companies, Coca-Cola and Britvic, reduced the average amount of sugar in their drinks by 17% and 26% respectively; however, the sugar content of their flagship products, Coca-Cola and Pepsi, remained unchanged.

The data revealed that 73% of the sugar reduction was due to reformulation of existing products or the introduction of new, lower sugar drinks, while 27% was due to changes in consumer purchasing behaviour.

Lead researcher Lauren Bandy said the figures were “striking”.

“It is encouraging to see such a large reduction in sugars sold in soft drinks,” Ms Bandy said.

“This is largely a result of change in the composition of drinks but there have also been shifts in consumer purchasing behaviour, with more consumers choosing drinks with low, or no, sugar content.

“They show that it is possible for improvements in public health to be consistent with successful business practices.”

Co-author Susan Jebb said she hoped the results would encourage more of the food industry to adopt healthier practices.

“National and international governments are calling for change in the food industry to improve public health,” she said.

“This new method allows researchers to monitor the progress being made and to make this information available to the public.

“This external scrutiny will hopefully encourage more positive and rapid action by the food industry to achieve healthier diets.”