Public Health England says changes to nine food groups could lead to 200,000 tons of sugar being taken out of snacks yearly by 2020

Chocolate bars and sweets are likely to get smaller as a result of a major push from Public Health England, which is urging the food industry to help fight obesity by cutting 20% of sugar from the main snacks and foods that children eat.

After talks with the confectionery industry, which has said removing sugar and keeping the taste would be hard, PHE is recommending they make the change by shrinking the size of the sweets and chocolate bars they sell.

PHE says changes to nine food groups could lead to 200,000 tons of sugar being taken out of snacks and meals yearly by 2020 and cut the number of overweight children by 20%. The targets are biscuits, breakfast cereals, cakes and pastries, chocolate, confectionery, ice cream, puddings, sweet spreads and yoghurts.

But the agreement is voluntary and some obesity campaigners warn that food manufacturers and restaurants may drag their feet unless there is a way to force their compliance.

“We’ve seen over recent weeks that some companies within the food and drink industry have made great progress whilst others are seriously lagging behind and others claiming wrongly that they can’t do it,” said Graham MacGregor, a professor of cardiovascular medicine and chairman of the campaigning group Action on Sugar.

“If these recalcitrant companies don’t comply we need Theresa May to bring in tough measures to ensure compliance and put public health first before the profits of the food industry.”

The 20% cut in sugar from foods, along with the sugar levy on soft drinks, were the two measures recommended by PHE and accepted by the government for inclusion in the national obesity plan published last summer. The government has since been criticised for rejecting other measures PHE recommended on more curbs on advertising to children and an end to multi-buy and discounted promotions of junk food in supermarkets such as buy one, get one free.

Duncan Selbie, chief executive of PHE, said they had never advised government that the sugar cuts should be compulsory. “We didn’t want to spend the next two or three years arguing whether a Jaffa Cake was a biscuit in judicial review,” he said.

Manufacturers and retailers had responded well to the proposed voluntary measures. “With a few exceptions, they have engaged very positively in this,” he said. “In the event that we don’t see progress we will be giving advice to the government about what further they might need to do.” He would not comment on what that might be, however.

Alison Tedstone, chief nutritionist, said PHE would be publishing a “barometer” of the top 20 products children consume, showing whether the sugar levels were coming down. “Parents will be able to see,” she said. “We will put it straight into the public domain.”

But while the PHE targets and transparency were widely welcomed, critics questioned whether the food industry and retailers and restaurants would comply.

“If we’re serious about changing the nation’s sweet tooth, industry as a whole needs to commit to the government’s very welcome 20% target and take collective responsibility for change,” said Professor Russell Viner of the Royal College of Paediatrics and Child Health. “The noises coming from certain companies remain a concern, with some hoping that a 10% reduction in sugar will somehow get them off the hook of the proposed 20%. The government must keep a close eye on how industry is acting and be tough on those who claim lower targets should be deemed a success.”

Alison Cox of Cancer Research UK said: “It’s clear that obesity has a major impact on cancer risk. Without action, the problem is only going to get worse, so it’s vital this new programme works towards the goal of slashing the amount of sugar hidden in our food.”

The British Retail Consortium is concerned that removing sugar will be technically difficult and that some food companies will comply but others may opt out. “Significant progress has already been made but the complexity of the reformulation process gives us concern about the time scales. Furthermore, to achieve the objective as outlined by PHE, these targets need to create a level playing field for every food company, large or small, to commit to and address,” said Andrea Martinez-Inchausti, deputy director of food policy.

The Food and Drink Federation said it supported the PHE plan. “Today’s report represents a constructive platform on which to build a world-leading programme of voluntary sugars reduction, right across food and drink,” said the director general, Ian Wright. “All parts of the food industry – manufacturers, retailers, takeaways, restaurants and cafés – need to step up. The guidelines are very stretching but manufacturers, for our part, are willing to take on the challenge.”

PHE has warned that saturated fat should not be substituted for sugar. It will be extending the work to produce targets and guidelines for cutting calories generally from food. Next year, after a report that is anticipated from the government’s standing advisory committee on nutrition, it may turn its attention to reducing saturated fat in foods.