The company that makes chocolate bars such as Mars and Snickers, is to stop targeting its advertising at under-12s.
Masterfoods core confectionery products will not be targeted at under-12s
Masterfoods will stop advertising in magazines and television programmes intended for children under the age of 12 by the end of the year.
Masterfoods, which also makes Twix and Maltesers, already has a policy of not targeting children under six.
The move comes after TV watchdog Ofcom said it would ban junk food advertising during TV shows aimed at under-16s.
In the November announcement, the regulator also warned that it would ban such adverts during adult programmes that are watched by a lot of children.
There have been suggestions that Masterfoods is taking action voluntarily before it is forced to by regulators, either in the UK or in Europe.
Jeremy Baker from London Metropolitan University says "they're being forced to do this by Ofcom anyway and now they're making a good PR gesture out of it".
Age for protection
Masterfoods may also be trying to make a statement about which age-groups need protecting, experts said.
Ofcom plans to ban junk food advertising from programmes aimed at children under-16, while Masterfoods' unilateral ban targets children under-12.
"There's no evidence whatsoever that under 16-year-olds need protecting from this kind of advertising," said Hamish Pringle from the Institute of Practitioners in Advertising.
Masterfoods' new policy will also cover websites targeted at children.
It is unclear how the company will prevent children gaining access to sites promoting its products, but some of its websites currently offer games and screensavers for children.
'Measures too broad'
When Ofcom's measures are brought in a Food Standards Agency (FSA) ratings system will be used to assess which foods are too high in fat, sugar and salt to be advertised to children.
But there have been some complaints that the system would also outlaw advertising for some popular products.
For example, the FSA's measure would lead to adverts for cheese, honey and Marmite being banned, the Grocer magazine said.
News of Masterfoods' decision comes as the European Union's committee on diet, physical activity and health is meeting in Brussels to discuss what progress companies are making on self-regulation.