Just over the half of the delegates, 52%, voted in favour of the motion: 'It is time to consider a ban on marketing to children'. The result signals a shift from the traditional Tory position of favouring limited state intervention.
The debate was the first of its kind in a series of interactive discussions highlighting key issues. Delegates voted by keypad and could text their views, which were displayed on the screen in the main hall.
Nick Stace, director of campaigns and communications at Which?, spoke in favour of the motion, focusing on junk-food advertising. He revealed the results of a YouGov poll, commissioned by Which?, that found strong support for the prevention of marketing unhealthy foods to children.
According to the survey, 80% of the 2160 respondents agreed that TV ads promoting unhealthy food should not be permitted to air during times when children were most likely to be watching. It also found that 91% agreed that food firms need to be more responsible in the way they market food to children.
'If political parties want to champion issues that matter to the public, then ending marketing of unhealthy food to kids is a first step,' he said.
Speaking against the motion, Janet Daley, a Daily Telegraph columnist, said legislation was not needed and parents should take more responsibility.