Pupils should be banned from leaving school at lunchtime to prevent them eating junk food, the School Food Trust has said.

A report by the government-funded trust found secondary schools had an average of 23 junk food outlets within a mile of the school.

“Schools have to compete with myriad takeaways, chippies and sweet shops for pupils' dinner money,” said School Food Trust CEO Judy Haragon. “Some children will go for chips five times a week if they are allowed to. This is damaging their long-term health and threatening the viability of school lunch services.”