Sweet-toothed consumers face paying more for bottled milkshakes and some fizzy drinks after the government confirmed plans for a tougher sugar tax.

Designed to tackle obesity, the levy currently applies to drinks with a sugar content of 5g per 100ml. However, after a public consultation this is being cut to 4.5g per 100ml, meaning it could cover hundreds more products.

The health secretary, Wes Streeting, told the Commons on Tuesday that an exemption for milk-based drinks would also end.

“We’re expanding the soft drinks industry levy to include bottles and cartons of milkshakes, flavoured milk and milk-substitute drinks,” he said. “This government will not look away as children get unhealthier and our political opponents urge us to leave them behind.”

The changes will not happen immediately. There will be another consultation before the legislation takes effect on 1 January 2028. This gives drinks makers two years to change their recipes.

Officially called the soft drinks industry levy (SDIL), the tax applies to most sugary and fizzy soft drinks sold in cans, bottles and cartons in supermarkets.

Previously, milk-based drinks were exempt because they contain calcium, which is encouraged in children’s and young people’s diets. However, the high sugar content of some of these drinks has prompted the rethink. A “lactose allowance” will factor in the presence of naturally occurring sugars in milk.

The tax does not apply to drinks made and served in cafes, restaurants and bars, which means milkshakes, lattes and hot chocolates served on the high street are not affected.

The sugar tax was introduced by George Osborne in 2016 to tackle rising levels of obesity and has been deemed a success as it prompted many drinks makers to change their recipes.

Between 2015 and 2019, about 65% of soft drinks that contained more than 5g of sugar per 100ml were reformulated to fall below the threshold. Today, almost 90% of the drinks on sale contain less sugar than the level at which the tax applies.

The government originally considered whether to lower the threshold to 4g of sugar per 100ml. Gavin Partington, the director general of the British Soft Drinks Association, said the reset would be an “additional cost burden” for the industry but took “comfort” that the government did not go further.

skip past newsletter promotion

Sign up to Business Today

Get set for the working day – we’ll point you to all the business news and analysis you need every morning

Privacy Notice: Newsletters may contain information about charities, online ads, and content funded by outside parties. If you do not have an account, we will create a guest account for you on theguardian.com to send you this newsletter. You can complete full registration at any time. For more information about how we use your data see our Privacy Policy. We use Google reCaptcha to protect our website and the Google Privacy Policy and Terms of Service apply.

Drinks makers had told officials they would struggle to come up with new, lower-sugar recipes, with drinks containing between 4g and 5g at the limit of what was technically possible. Beyond that, there would be problems around taste for consumers.

Dentists welcomed the tougher rules. Dr Charlotte Eckhardt, the dean of the faculty of dental surgery (FDS) at the Royal College of Surgeons of England, described the new parameters as a “significant victory for public health”.

The FDS had campaigned for a cut to 4g but Eckhardt said extending the levy “represents a major step towards protecting children’s oral health”.

“Tooth decay remains the leading cause of hospital admissions among five- to nine-year-olds in England, outpacing other illnesses such as acute tonsilitis,” she said.

At present, the tax is charged at 18p a litre on drinks containing at least 5g of total sugar per 100ml, and 24p a litre on drinks with 8g of sugar or more. The changes to the levy are expected to raise up to £45m a year for the Treasury.