In a surprise move, representatives at the Tory conference in Bournemouth voted by 52 per cent to 48 per cent for a motion saying: "It's time to consider a ban on marketing to children."
The vote was seen as further evidence that a political consensus is developing in favour of tougher action on junk food and other ads.
In the past, the Tories have been regarded as a pro-business party opposed to state regulation. The Tory leader, David Cameron, said he had always opposed a ban based on his experience as the director of corporate affairs at Carlton Communications, but agreed that one should now be considered. He said: "We need responsible advertising and not advertising that plays on pester power."
The Tories voted for the motion after the case for a ban was put to the conference by Nick Stace, the director of campaigns and communications at the Consumers Association. He argued supporting a ban would help the party win the next general election. Stace said: "We are the fat man of Europe. We need to tackle the obesity crisis. Advertising is not the only way, but it is one important way."
The case against was put by Janet Daley, a columnist from The Daily Telegraph. She argued that parents would be bad role models for their children if they couldn't teach them to resist temptation and had to rely on the state.