Fast-food takeaways will be banned from opening within 400 metres of schools in a bid to tackle the capital’s child obesity epidemic.
In addition, all new chicken, fish and chip and pizza outlets will have to sign up to minimum healthy food standards before getting planning permission.
Sadiq Khan will announce the policy in his draft London Plan, the capital’s “planning bible”, due to be published later this week.
The Mayor said the move would help deal with the “ticking time bomb” of childhood obesity in London, where almost 40 per cent of children are obese or overweight by the time they finish primary school, the highest proportion in England.
Several boroughs, including Barking and Dagenham, Islington and Waltham Forest, already have measures to control chicken shops, chip shops and takeaways near schools.
Mr Khan’s plan states that new takeaways should not be permitted within 400 metres of an existing or proposed primary or secondary school.
The Mayor is also bringing in a new health standard so new takeaways have to agree to make food healthier by grilling or baking instead of frying and adding less salt.
He said: “Takeaway restaurants are a vibrant part of London life, but it’s important that they are not encouraging our children to make poor food choices.
“I am using all of my powers through my new London Plan to prevent new takeaways from being built just down the road from schools as part of a package of measures to tackle the ticking time bomb of childhood obesity and help us all lead healthier lives.”
Overweight children are more likely to miss school due to illness and to develop type 2 diabetes, heart disease and strokes as adults.
Dr Yvonne Doyle, London regional director at Public Health England, said: “Our high streets are increasingly saturated with takeaways and our school children consume too much unhealthy food and drink on the high streets near schools.
“This plan will encourage a healthier food environment around our schools so that junk food is no longer the option for children nearest the school gates.”
Mr Khan will also use the London Plan to commit to protect the greenbelt.
His new planning policy is also expected to call 50 per cent of all new homes across London to be affordable, while private housebuilders would work towards a 35 per cent requirement.
The Mayor has also said the target for the number of homes built every year will rise from 29,000 to 66,000, although housing experts doubt whether this is achievable.