Nick Stace, Which? campaigns and communications director, made the call at the Conservative Party Conference today in Bournemouth.
Speaking in this morning's Hot Topic debate on the motion "It's time to consider a ban on marketing to children", Stace said that it was an issue that was significant to the electorate.
Stace said: "If political parties want to champion issues that matter to the public then an end to the marketing of unhealthy food to children is a first step.
"Thousands have joined the Which? campaign to force food companies to act more responsibly and this latest poll shows that this is a significant issue to the electorate -- with the majority wanting an end to the promotion of unhealthy foods to kids. Politicians ignore this at their peril."
However, Andrew Brown, the AA's director-general, rejected the call and said that the state alone could not solve the problem.
He said: "State intervention alone will not solve the challenges society faces on issues like obesity. David Cameron yesterday talked about the importance of corporate, social and individual responsibility to achieve real changes in behaviour, rather than just ticking boxes through regulation.
"The food industry is committed to working in partnership with all the stakeholders to tackle the obesity problems," he said.
He also criticised Stace for saying that the present codes governing the promotion of products to children were only voluntary.
While food manufacturers, as well as broadcasters and the advertising industry, are still fighting against a ban on TV ads for unhealthy foods before the 9pm watershed, health campaigners are looking at bringing about much wider restrictions.
It was revealed last week that a campaign to ban all forms of advertising aimed at the under-12s is to be launched by Labour Party activists, religious and pressure groups.
Stace told delegates at the Tory conference that four in five voters want television ads for junk food stopped and that 91% of people agree that food companies need to be more responsible in the way they market food to children.
Which? based its research on a poll of 2,160 people on YouGov.
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