Youngsters who sit up with their parents and watch prime time TV are being "saturated" with junk food ads, a charity has warned.
People who watch television between 8pm and 9pm can see as many as 11 junk food adverts an hour, the British Heart Foundation (BHF) said.
The charity reported that analysis of more than 750 adverts from prime time television found that 22% were for food.
More than one in 10 (13%) of the food ads were for fast food chains and 12% were for chocolate and sweet companies, according to the research.
And a quarter of food adverts were for "unhealthy food products from supermarkets", BHF said.
The authors of the research reported that the food adverts "seem" to be designed for a young audience, with more than half of ads using children, or "child-aged characters", to promote the food.
The charity is leading a group of organisations , collectively called Action on Junk Food Marketing, which commissioned the research .
The alliance have called for the Government and Ofcom to take action.
They have also launched a new petition calling for m inisters to ban junk food marketing for children.
"Parents don't expect their children to be bombarded with ads for unhealthy food during prime time TV, but that's exactly what happens," BHF chief executive Simon Gillespie said.
"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."
Professor Mitch Blair, officer for health promotion at the Royal College of Paediatrics and Child Health, added: " Currently junk food advertising on television is banned during children's programming - but we know that millions of children are watching 'family friendly' programmes like the X Factor and Ant & Dec's Saturday Night Takeaway later in the evening.
"And we know that advertising to this age group at this time, works; not only are children and young people easily influenced and parents worn down by pester power, but food companies wouldn't spend huge amounts of money if it wasn't effective.
"Extending the ban to 9pm would not only have a positive effect in changing behaviours, but it would also send a clear message to the industry.
"Children should not be commercially exploited and the advertising industry must take some responsibility for helping tackle the growing problem of childhood obesity."
A Government spokesman said: "The Government continues to keep this area under review and recognises that there are calls for increased restrictions on junk food advertising.
"It is widely accepted that advertising is just one aspect in determining children's choice of food, and the current rules are therefore just one part of the package aimed at tackling childhood obesity and poor diet.
"The Government is taking action, including through Change4Life and the Responsibility Deal, to ensure children get the best start possible in life and to make it easier for families to make healthier choices and follow a balanced diet."
Shadow public health minister Luciana Berger said: "One third of children in England are either overweight or obese by the time they leave primary school and the Government should be doing everything it can to tackle this crisis.
"Yet every day children are being exposed to persuasive adverts for foods and drinks that are high in fat, sugar or salt - the very ingredients from which the current regulations were designed to protect them.
"With health problems associated with being overweight or obese costing the NHS more than £5 billion every year, ministers must act now to ensure that the rules around advertising junk food to children are fit for purpose."
:: To sign the alliance's petition, visit bhf.org.uk/ditchthejunk