The report by The Food Foundation charity, released on Wednesday, concludes that "aggressive" marketing of cheap, ultra-processed food together with diets lacking nutrition—often fuelled by poverty as well as the food industry—are behind a "significant decline" in children's health.

It finds that British children have been getting shorter, on average, since 2013, after being on an upward trajectory since 2000. While acknowledging that ethnicity plays a role in height, the report says data suggest the decline is more down to dietary deficiencies than to shifting demographics.

Meanwhile, obesity levels in 10- and 11-year-olds have increased by 30 percent since 2006, while Type 2 diabetes in the under-25s has increased by 22 percent in the past five years.

Anna Taylor, executive director at The Food Foundation, said in a statement: "The health problems being suffered by the UK's children due to poor diet are entirely preventable.

"Politicians across the political spectrum must prioritise policies that give all children access to the nutrition they need to grow up healthily, as should be their right."

Childhood Obesity Could Cost £8 Billion

Experts suggest current levels of childhood obesity could cost the country in the region of £8 billion through the burden on the NHS and the benefits system if a larger percentage of the population ends up unfit for work.

The Food Foundation has its own "election manifesto" urging incoming MPs to do more to ensure that good quality food is more readily available and affordable to all, as it says obesity and food related illnesses are preventable.