A crackdown on junk food advertising to children will not be effective as the programmes most watched by children will not be covered, campaigners say.
The restrictions focus on foods high in salt, fat and sugar
Ads for unhealthy food are to be banned from the end of March during TV shows targeted at under-16s, Ofcom has said.
But consumer group Which? said the plan was flawed after finding the 20 ITV1 programmes most watched by under 16s in October would not be affected.
Ofcom said its proposals had to be "targeted and proportionate".
Ads are to be banned during children's programmes, on children's channels and programmes watched by a higher than average number of children.
This is likely to cost broadcasters an estimated £39m in lost advertising revenue, according to the regulator.
The measures fall short of the pre 9pm blanket ban demanded by campaigners.
However, Ofcom still went further than expected. It had been initially considering a ban on junk food advertising during programmes aimed at under-nines, before increasing it to under 16s.
Despite this, the wording means TV favourites such as Coronation Street and the X Factor are not covered by the ban.
The research, carried out during a two-week period in October, showed that the most-watched programme that would face an junk food ad ban would be Spongebob Squarepants in 27th place which had 170,000 child viewers.
More than 1.1m children watched Ant and Dec's Saturday Night Takeaway and over 800,000 tuned into Coronation Street.
More children even watched shows like Parkinson and ITV Evening News than Spongebob Squarepants.
Which? chief policy adviser Sue Davies said: "While Ofcom has recognised that its objective should be to protect children under 16, its proposed approach is completely flawed.
"Producers of foods high in fat, sugar and salt will still be free to advertise their products during the programmes most children are watching."
The Food and Drink Federation said it could not comment on the research, but said it still felt the proposals had gone too far.
A spokeswoman said: "We are currently consulting our members and will be submitting a formal response later."
An Ofcom spokesman said: "For every child watching the programmes listed there is typically nine adults.
"It would not be targeted or proportionate to impose a blanket ban before 9pm."