Health campaigners have called for food and snack makers to be banned from advertising food high in fat, sugar and salt before the 9pm watershed after new analysis of TV adverts found almost one in four ads shown between 8pm and 9pm were for food (22%), with viewers seeing as many as eleven junk food adverts per hour.

The new research from campaign group Action on Junk Food Marketing, whose members include the Children’s Food Campaign and the British Heart Foundation, found that nearly a third (31%) of food adverts shown between eight and nine pm use themes of ‘fun’ and over half used children or child-aged characters to promote their food (53%).

The analysis, which was carried out by researchers at the University of Liverpool, found that unhealthy food items accounted for 11% of all adverts and around half of all food adverts.

They said the most frequently shown adverts for unhealthy food products came from supermarkets such as Aldi and Morrisons, followed by fast food chains such as Domino’s and KFC.

Around a third of ads ended with a website or Twitter hashtag - a key way of reaching teenagers.

Simon Gillespie, chief executive of the British Heart Foundation, said: “Parents don’t expect their children to be bombarded with ads for unhealthy food during primetime TV, but that’s exactly what happens.

“Even when the show is over, junk food marketers could be reaching out to young people online. A lack of regulation means companies are free to lure kids into playing games and entering competitions – all with a view to pushing their product.

“We want the Government to protect children by switching off junk food adverts on TV until after 9pm and putting rules in place to stop children becoming fair game for internet marketing.”