Plans to curb food advertising aimed at children are being unveiled by Ofcom.
Almost a third of children in the UK are now overweight
The media regulator has ruled out a total TV advertising ban, but is launching a 10-week consultation on guidelines restricting the adverts.
The government's White Paper on public health said children should not be encouraged to eat too many foods high in fat, salt and sugar.
But the British Heart Foundation and consumer groups said Ofcom's proposals did not go far enough.
It called for a complete ban on all junk food broadcast advertising before the 9pm watershed.
"Without such radical measures, the government will have little hope of reaching its target to halt the growth in childhood obesity by 2010," said Josh Bayly, campaigns officer for the foundation.
Current estimates suggest just under a third of those under 16 are now overweight, and 17% are obese.
Any changes to food promotion must be introduced by next year, the White Paper says.
Under the plans, celebrities and characters from films or TV programmes would not be allowed to take part in any food or drink commercial targeted at the under-10s.
Adverts showing excessive consumption would also be discouraged.
Ofcom research indicates TV adverts have a "modest direct effect" on children's food choice.
But the combination of exercise, family eating patterns and school policy plays a much larger role in childhood obesity, according to the regulator.
Ofcom's proposals are expected to restrict food and drink adverts aimed at children, but fall short of banning them altogether.
Public Health Minister Caroline Flint said the government was "committed to changing the nature and balance of food promotion to children".
"We want to support parents in protecting their children from encouragement to eat too many high fat, salt and sugar foods.
"We will await with interest the outcome of Ofcom's consultation on how to further restrict such advertising on television."
The National Consumer Council has called on Ofcom to ban adverts for foods high in fat, salt and sugar from TV shows aimed at children under the age of 16.
Its food expert Sue Dibb added: "Anything less than full restrictions on all TV ads and promotions for high fat, salt and sugar foods before the 9pm watershed will be extremely disappointing."
Food and farming alliance Sustain spokesman Richard Watts said: "Unless kids are protected from junk food adverts during programmes like X Factor, the Bill or I'm a Celebrity... new rules will be meaningless."
A coalition of multi-national food companies, advertising agencies and the broadcast media, the Food Advertising Unit, said advertising targeting children needed to change.
But other measures would be needed to change eating habits and tackle childhood obesity in the long term, it added.
Food and Drink Federation director general Melanie Leech said the food and drink manufacturing industry recognised "a range of concerns relating to advertising and promotion to children".
"As set out in our food and health manifesto, we are committed to working with Ofcom and government, and we will study the detail of the consultation and respond in due course," she said.