"The problem with the pre-9pm ban is it’s arbitrary, really," McCall said. "It’s not going to be effective, and it’s not going to change behaviour. It’s just a kind of weapon, that goes, 'we’re going to bash this'."
She also objected to TV being singled out: "There isn’t a 9pm watershed in any other media – there isn’t one on Facebook or Google, on posters or in magazines. It’s just an odd thing is this day and age to be thinking about."
The restriction is supported by a range of charities, campaigners including Jamie Oliver, and MPs from both major parties. It would affect hit ITV shows that cater to a family audience such as Britain’s Got Talent and Ant & Dec’s Saturday Night Takeaway.
But the idea has been criticised by the Advertising Association, which says evidence suggests that advertising has only a small impact on dietary behaviour, and other steps would be much more effective in tackling obesity.
Speaking at Media 360 in Brighton, where she was interviewed on stage by Campaign’s editor-in-chief Claire Beale, McCall acknowledged that obesity was a "massive problem" for the UK, which has some of the highest rates in the world for both childhood and overall obesity.
"We have to be very clear that we’re an ally to changing behaviour, rather than someone to be punished for doing nothing but being media," she said.
But, while media had a role to play in encouraging better diets, McCall described the right approach as being about "getting people to see that having a burger or a pizza, or whatever, is part of what you eat, not all of what you eat.
"TV can help on behaviour change – through its programmes; soaps, for instance. And it can get the nation moving." ITV is supporting a national initiative called The Daily Mile, which aims to get children at every primary school in the UK to run or jog for 15 minutes each day.
McCall added that ITV would "try very, very hard" to persuade food and drink manufacturers to reformulate their products to remove sugar, salt and fat. "They have got to think about that or they’re going to be taxed in different ways," she said, referring to the sugar tax that recently came into force.