Charity The Food Foundation also blamed and the "aggressive promotion of cheap junk food" for a perceived deterioration in children's health and wellbeing.

Its report states the average height of five-year-olds has fallen year-on-year since 2013 with boys and girls in the UK ranked the shortest and second shortest in comparison to other high-income countries, based on data from the Non-Communicable Diseases Risk Factor Collaboration - a network of health scientists.

Obesity among 10-11-year-olds has also increased by 30% since 2006, with one in five children classed as obese by the time they leave primary school, the report found, citing data from the National Child Measurement Programme.

Diet-related illnesses such as Type 2 diabetes has also seen a rise in under 25s, up by 22% in the past five years, the Food Foundation says, using data from the National Diabetes Audit 2021-2022.

The NHS classes a child or teenager as very overweight if their body mass index (BMI) is more than 98 out of 100 others in the same age category.

Campaigners from the charity said the cost of living crisis has exacerbated the problem, and called for action from the next government to "reverse the current trajectory".

It said failure to take action "will lead to a generation burdened throughout their lives by diet-related illness and the consequences that brings with it" including on mental health and the NHS.

Last month, analysis by Germany-based life sciences consultancy stradoo, found that severely obese young children could cut their life expectancy by around half.

The research found children who were severely obese by age four, with a BMI z score of 3.5, had a life expectancy of 39 if they didn't lose weight, while children with a score of 2.5 had one of 50 years.

Children 'deserve so much more'

Commenting on the report, celebrity chef Jamie Oliver said children "deserve so much more" and said change needs to improve "the quality of food across the board".

"The [prime minister] who understands this and gets serious about child health will be the person who turned the tide on obesity - and won," he said.

Last year, a ban on two-for-one junk food deals was delayed by the government for the second time until 2025 to avoid restricting consumer options while prices remain high.

The buy one get one free (BOGOF) ban, which formed part of the anti-obesity strategy, had already been pushed back from October 2023, fuelling speculation that it could be dropped completely.

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Among those calling for more urgent action on child health is former prime minister Gordon Brown, who said: "Every mother and father in the land will be concerned and shocked at what is happening to children through lack of nutrition living through the hungry 2020s in food bank Britain."

Professor Sir Michael Marmot, director of the UCL Institute of Health Equity, added: "We used to think of the combination of undernutrition and obesity as a feature of low and middle income countries. We are now seeing it in Britain in 2024, a devastating effect of poverty."