Labour is "looking at" restrictions on advertising of e-cigarettes because of concerns that they may lead to children taking up smoking, shadow health secretary Andy Burnham has said.
Mr Burnham said there was "absolutely no doubt" that the electronic devices were a "gateway product", and questioned whether it was acceptable for them to be exempted from the ban on cigarette advertising.
The shadow health secretary was speaking shortly before the publication of a Labour public health paper, which he said would set out an "unapologetic, firm and decisive" case for state intervention to improve children's diet and tackle problems with smoking and cheap alcohol.
The paper is expected to include a cap on sugar content in children's breakfast cereals, which was floated by Mr Burnham last year.
Mr Burnham told The House magazine that the Government had been wrong to adopt a "finger wagging" approach to public health, trying to encourage healthier lifestyles by persuasion and striking voluntary agreements with the industry.
He accused ministers of "a real loss of leadership on public health", including by failing to implement plain packaging for cigarettes.
"I think the finger wagging nanny state message does turn people off," he said.
"You know 'don't do this, don't do that'.
"That's run its course.
"We're saying it's absolutely right for the state to intervene - and probably do so even more decisively than we did when we were in government - to protect children.
"Because children don't control the situations they're exposed to, the environment they're exposed to or the food that's put down to them.
"Therefore I do think the state has an absolutely clear moral and intellectual basis for saying 'we will act to protect all children'."
Mr Burnham said he was concerned to hear from his son that pupils were smoking e-cigarettes at school because they were easier to conceal from teachers than regular cigarettes, but were then smoking tobacco outside school.
He said: "It's a difficult one.
"My son is 14, he's really clear that kids are doing it at school.
"You can hide it.
"But he's clear that the kids who've done it are then smoking outside of school.
"There's absolutely no doubt about it - they are a gateway product.
"But then other people say they've helped with smoking cessation.
"There's a lot of evidence to support that, and we don't want to lose those benefits.
"So I think we'll tread carefully.
"But I'm troubled by some of the advertising of them.
"I think they're exploiting some loopholes there in terms of advertising.
"I've noticed at (Everton football grond) Goodison Park, it's all round the perimeter all the time.
"Given they are a product that is leading people to smoking, and given we've banned (tobacco advertising) 15 years ago, is it now acceptable for that?
"So I am looking at that."
Asked whether he would to press ahead with plans to cap the amount of sugar in breakfast cereals, Mr Burnham said: "I'm not comfortable with the idea that any child in my constituency sits down at breakfast time to a bowl of food that is 38% sugar.
"And if people are comfortable with that, I'm going to disagree with them.
"I don't think any child should be regularly taking in sugar of that level."
Mr Burnham indicated that his actions would not be so draconian as to outlaw breakfast-time favourites Frosties, saying: "I don't think it would be that bad.
"They would still exist - I can confirm that."
He added: "When we launch our public health paper in a couple of weeks... we're going to take it as an opportunity to reframe the debate on public health, to set out a new approach on public health from Labour.
"This isn't anti-business, or anything like that.
"The Responsibility Deal, the Government's approach, just really hasn't worked, because the minute one company says `Well, actually we're peeling away', it kind of goes.
"Because the market takes hold and you don't make progress."
Mr Burnham ruled out proposals for a "sugar tax", saying that he did not want to go down the road of taxing food.
"I don't think we could justify in any way a tax on healthy food," he said.
"I couldn't accept that, and it's just not something that would fit well with any Labour person - taxing food.
"So I've always been pretty clear that that isn't the answer.
"But there is a problem with rising levels of sugar in people's diets.
"Sugar particularly, but also fat and salt."
He said that the industry wanted clarity about what was allowed, in order to compete on a level playing field.
On a possible sugar cap, he said: "I think the issue for them would be well what level would you set it?
"But we will consult really carefully with them about all of that."
He said his wife Marie-France had alerted him to the levels of sugar in some cereals: "You buy some of the products that look as though they're slightly healthier, they've got grain in or whatever, they don't have 'sugar' in their name on the box.
"But you look at them and go 'Oh my God, it's loaded!'
"In the old days we had it from the bowl on the table, on your Weetabix.
"It's built in now isn't it?
"So I just don't think people are able to monitor and control the amount of sugar that they're taking."