Video: The hidden dangers of your child's packed lunch

A study published today shows only one-in-five lunch boxes of eight- and nine-year-old pupils contains any vegetables, while more than three quarters include foods high in saturated fat, salt and sugar, such as crisps, sweets and biscuits.

Leeds University academics analysed the content of the packed lunches of around 1,300 children from 89 schools across the UK.

School lunches must contain protein-rich and low-fat starchy foods, vegetables, fruit and dairy products. Meals cannot include sweets, savoury snacks or artificially sweetened drinks.

Leeds University researchers say just 1.1 per cent of the packed lunches they assessed meets these standards.

Around half of the country's school children opt for a packed lunch – around 5.5bn meals every year.

Professor Janet Cade, head of the Nutritional Epidemiology Group at Leeds said: "The poor quality of these meals could have serious implications for levels of childhood obesity and its long-term consequences."