Health experts have called on schools to keep their pupils' on-campus during lunch breaks, stopping them from purchasing junk food outside of the school grounds.

Despite recent moves to make school dinners more healthy, many pupils are still opting to visit local junk food establishments, buying fatty foods such as burgers, chips and kebabs to satisfy their hunger.

A study from the London Environmental Health Food Teams found that many of the pupils' favourite junk foods had over two thirds of the recommended calorie intake for an adult man, containing higher levels of salt than the daily recommended allowance.

Instead of letting schoolchildren off the school premises at lunch, campaigners care urging schools to keep pupils on the grounds, offering them healthy but interesting lunch options as well as allowing packed lunches. With advice from those in dietitian jobs and the high profile of chef Jamie Oliver's school dinners initiative, it is hoped that more schools will embrace healthy eating plans.

School Food Trust's chairman, Rob Rees believes that parents could be unaware that their children have received more than their daily helping of fat and salt, leaving them open to consuming more fatty foods after school. Nevertheless, he acknowledges that schools are making an effort to provide a healthy option that is competition to high street junk foods.

Rees was cited in The Telegraph as saying: ''It's vital that [healthy eating programmes in schools] are not undermined by nearby junk food outlets - that's why we support stay on site policies and steps to limit access to takeaway food around schools.''