Banning junk food adverts during children’s television programmes would not work, claimed a television watchdog.

A health white paper, set to be published by the government tomorrow, is expected to threaten a ban on adverts during certain times of the day if manufacturers and advertisers fail to agree a voluntary code.

However television regulator Ofcom said it conducted research into the subject early in the year which it claimed showed television advertising had only a modest effect on children’s food consumption.

Similar bans in other countries were “both unclear and untested” it added. Ofcom places the main blame for obesity on lack of exercise, family eating trends and food labelling.

The white paper is also expected to introduce a new system of labelling to highlight unhealthy foods.