A group of 40 health groups and academics have called on the Government to release a delayed report into one of its flagship sugar reduction strategies following a recent increase in obesity prevalence among primary school children.

The sugar reduction report, which was due to be published last year, is expected to provide further evidence of the success of the soft drinks industry levy since its introduction four years ago today, while also exposing a “dismaying lack of progress” in most other product categories covered by the voluntary reduction programme, the campaigners said.

The group, which includes the Obesity Health Alliance, British Heart Foundation, Royal Society for Public Health and the British Dental Association, have written to Health Secretary Sajid Javid calling on the Government to stop delaying publication of the final report.

In the letter, the organisations point to the “very worrying” recent increase in obesity prevalence among primary school children and the urgency of addressing increasing health disparities which have been exacerbated during the Covid-19 pandemic.

They argue that evidence from the final report is vital to inform the next steps in mandating further industry-wide reform towards healthier food and drink.

Barbara Crowther, children’s food campaign co-ordinator at Sustain, said: “This report is already six months overdue, and with childhood obesity prevalence rising sharply, we should not be wasting any more time.

“We believe it will reveal the industry leaders and laggards on sugar reduction, and where further mandatory mechanisms need to be targeted.

“It’s crystal clear that when the Government legislates, as it did with the soft drinks industry levy, much faster and deeper progress occurs. We hope the Government will mark this anniversary by committing to publish the final sugar reduction report without any further delay.”

The soft drinks industry levy, which came into force on April 6 2018, removed 48,000 metric tonnes of sugar per year from soft drinks from 2015 to 2019, according to the previous 2020 interim sugar reduction report.

Independent academic evaluations suggest the levy has delivered a 30g per household per week decline in sugar consumed in soft drinks, with the largest effects seen in lowest income households who are disproportionately exposed to risks leading to poor health and being overweight.

The sugar reduction programme, which was one of the key strategies along with the soft drinks levy launched under former prime minister Theresa May’s government, set out to slash sugar levels by 20% across a raft of products high in fat, salt and sugar in the main categories consumed by children by 2021.

However, the voluntary programme was plunged into crisis when the last update, in 2020, revealed some categories had seen “little or no progress”, while others had seen massive increases in sugar levels.

Some categories, such as chocolate and sweet confectionery, had seen sugar levels virtually unchanged, while increased sales had led to a massive increase in the volume of sugar sold.

Anna Taylor, executive director of The Food Foundation, said: “The soft drinks levy has been hugely successful in reducing the amount of sugar we drink, but we are still seeing soaring levels of childhood obesity.

“With rising food and fuel prices, the Government needs to urgently look at what it can do to drive reformulation across other food categories and rebalance the price of shopping baskets to ensure that healthier options, including fruit and vegetables, are affordable for everyone.

“Without this action, the obesity situation is likely to get significantly worse over the coming months.”

The delay to the report comes as campaigners and retailers also urge the Government to publish its promised response to Henry Dimbleby’s National Food Strategy, which came out last summer.

A Department of Health and Social Care spokeswoman said: “Obesity is one of the biggest health issues we face as a country, which is why we are delivering an ambitious programme of work which will empower adults and children to live healthier lives for longer, regardless of circumstance and background.

“Calorie labelling rules for large out-of-home food businesses come into force today, and we will be introducing restrictions on the promotion of products high in fat, salt and sugar, to support families to make healthier choices.”