BRITAIN needs to go on a diet, a top health official has said after it emerged some children are eating the equivalent of an extra meal a day in calories.

Public Health England (PHE) warned that obesity is becoming "the norm" as it challenged the food industry to cut a fifth of calories from popular family foods over the next six years.

As part of PHE's campaign to reduce the rising tide of childhood obesity, the health body has called on restaurants, retailers and manufacturers to slash the amount of calories in foods by 20 per cent by 2024, PHE said.

Duncan Selbie, chief executive at PHE, said: "Britain needs to go on a diet.

"The simple truth is on average we need to eat less. Children and adults routinely eat too many calories and it's why so many are overweight or obese.

"Industry can help families by finding innovative ways to lower the calories in the food we all enjoy."

It has estimated that some overweight or obese boys are consuming up to 500 additional calories a day compared to their normal weight peers and girls are eating almost 300 more calories.

PHE said that the food industry could cut calories by changing the ingredients of their products, reducing portion size or changing their marketing tactics.

The challenge involves 13 popular foods that families eat including: pizzas, savoury snacks, ready meals - including read-made sandwiches, some meat products, cooking sauces, chips and crisps and "composite salads" such as hummus or coleslaw.

PHE's chief nutritionist Dr Alison Tedstone said that these food groups had the "lion's share" of calories.

She said: "We have moved on from it [obesity] affecting a small section of society, it is the norm now."

She said: "When we look at overweight or obese children - basically a third of kids - we can see that they are consuming up to 500 calories a day more than they require.

"This is a lot of calories - 500 calories is an extra meal a day, it is a lot, and that's why we have an obesity problem in this country."

But PHE said if the 20 percent target is met within five years, then over the next 25 years more than 35,000 premature deaths could be prevented and the NHS and social care sector could save around £9 billion.

The health body pledged to hold the food industry to account and said that it will highlight calorie reduction progress among manufacturers or retailers.

A new campaign, One You, encourages people to only have 400 calories for breakfast, 600 for lunch and 600 for dinner.

Caroline Cerny, lead for the Obesity Health Alliance - a coalition of more than 40 health organisations and charities, said: "It's a real worry that this new data shows some children who are already an unhealthy weight eat the equivalent of an extra meal a day in calories.

"The food industry absolutely must play its part in tackling obesity, and through adapting recipes and reducing over-sized portions, can make it much easier for families to make healthier choices."