Professor Sir Albert Aynsley-Green, the children's commissioner, also called for tighter curbs on ads for unhealthy foods in magazines, posters, text messages, internet pop-ups, cartoon and film sponsorships and a ban on the use of celebrities.
His intervention is significant as it is the first time a government watchdog has backed the growing campaign by pressure groups for action on junk-food commercials. Ministers are resisting calls for a statutory approach.
Aynesley-Green spoke out after research by his office, based on interviews with 200 youngsters, found that ads were "drowning out" healthy-eating messages and left children confused.
Ellie Lewis, project development officer for the National Children's Bureau, which carried out the research, said: "Children and young people know that many of the foods and drinks heavily marketed to them are unhealthy, but the 'fun factor' used by advertisers often wins them over."