Children should be limited to two snacks of no more than 100 calories per day, according to a health body.

Public Health England (PHE) has warned that on average, children consume at least three unhealthy snacks and sugary drinks a day, with around a third consuming four or more.

That means children can easily consume three times more sugar than is recommended.

Its new Change4Life campaign calls for parents to "look for 100 calorie snacks, two a day max", to help offer healthier snacks to tackle the obesity epidemic which sees a third of children leave primary school overweight or obese.

PHE said half of children's sugar intake - around seven sugar cubes a day - comes from unhealthy snacks and drinks.

Each year, children consume almost 400 biscuits; more than 120 cakes, buns and pastries; around 100 portions of sweets, 70 chocolate bars and icecreams and more than 150 juice drink pouches and cans of fizzy drink, the campaign states.

It will give parents special offers on a range of healthier snacks, including fruit and vegetables, at selected supermarkets.

Among the suggested healthier options are fresh or tinned fruit salad, chopped vegetables and low fat hummus, plain rice cakes and malt loaf.

Dr Alison Tedstone, chief nutrionist at PHE, said "The true extent of children's snacking habits is greater than the odd biscuit or chocolate bar.

"Children are having unhealthy snacks throughout the day and parents have told us they're concerned.

"You see children buying chips coming out of school and buying a bag of chips on their way home from school, and that's part of the reason why we have an obesity epidemic in this country.

"To make it easier for busy families, we've developed a simple rule of thumb to help them move towards healthier snacking - look for 100 calories snacks, two a day max."

The campaign features a TV advert created by Aardman animations and will run across England for eight weeks from Tuesday.

PHE is working with the food industry to cut 20% of sugar from products consumed most by children by 2020.