The ban on advertising ‘junk food’ products across Transport for London’s out-of-home estate is well-intentioned but using such a crude mechanism to decide the fate of food and drink products means entire sectors of relatively harmless products are likely being banned.

From today (25 February), the restrictions will be in place on the London Underground, Overground, bus, rail, tram and road networks controlled by TfL.

Aimed at combating childhood obesity, this is an attempt to curtail a serious issue and the move has understandably been praised by Public Health England.

As a mum of two young kids I applaud the move to regulate in an attempt to reduce childhood obesity. However, I can’t help feel that the criteria by which products will be judged is too blunt a tool.

In fact, the new regulations could negatively impact children’s understanding of what constitutes a balanced diet and reduce the budget available to TfL as advertising monies are moved into other channels.

The crux of the problem with the ban is the score-based tool, created by Public Health England, used to decide the fate of products: foods are given a score based on the balance between beneficial nutrients, like fruit, vegetables and fibre, and ingredients which children should reduce in their diets, such as sugars and saturated fat and salt.

And the points-based system is product, not brand based, which means that McDonald’s can’t promote a Big Mac and fries but can its salads.

But how many people associate McDonald’s with salads?

Isn’t the likelihood that a family travelling on a London bus will glaze over the image of the salad and just see McDonald’s famous golden arches, next to which is a sign directing them to the nearest McDonald's, where they will go to eat Big Macs?

Likewise, Burger King, Deliveroo and Just Eat.

More worrying, though, is that this crude mechanism of judging food and drinks means that relatively harmless products, and even complete food ranges, could be banned completely.

For example, under the TfL rules, a kid’s dairy product (which Change4Life would say is a good sugar swap) would be banned, despite protein and calcium being essential and recommended to help kids grow.

Everyday household favourites like olive oil, yoghurt, butter and pesto would not be allowed while Macmillan Cancer Support could be prevented from promoting its coffee and cake events on the TfL network due to their sugar levels.

So TfL is banning charity and butter ads but permitting alcohol ads. And by banning ads for cheese, butter and olive oil, is TfL not in danger of preventing children from having a balanced diet?

The TfL planning document also says: "Incidental images, graphical representations and references to food and/or non-alcoholic drinks that promote the consumption of foods high in fat, sugar and salt will not be permitted."

This could mean that an advert for a travel company, which uses an image of people eating hotdogs, could be subject to the ban.

Outsmart, the trade body which represents outdoor advertising companies, says TfL could lose around £27m a year from the ban, a figure disputed by City Hall.

TfL has said some “less healthy” products may escape the ban if they can prove with evidence that they do not contribute to high fat, salt or sugar diets in children.

I can only envisage TfL being bombarded with brands arguing their case, costing it hours in manpower it can ill afford given its current finances.

Not only that, commuters could end up losing out, as lost revenue from advertising for TfL potentially could lead to passenger fares increasing.

For me, a better solution than a targeted junk food ban would be a more holistic approach – involving central and local government – like the one adopted in Amsterdam, to combat child obesity.

In Amsterdam, as well as banning ads for unhealthy food on its metro, the Dutch capital has also promoted the virtues of drinking tap water, extolled the benefits of after-school activity and refused sponsorship to events that take money from fast food brands. London would be better suited to copying this holistic model.

While I applaud Sadiq Khan for his ambition to curb child obesity in London, the mechanism he has chosen to achieve this is too blunt and flawed.

Ellie Roberts is head of planning at Bountiful Cow