London fast food
No new fats food restaurants will be allowed to open within 400 metres of a school Getty

The mayor of London has announced he is set to ban all fast food restaurants from opening within 400m (1312ft) of a school in order to crackdown on the "ticking time bomb" of childhood obesity.

Sadiq Khan will also reveal plans to force takeaway outlets to agree to prepare their food in healthier ways such as grilling or baking over frying and to use less salt.

Nearly 40% of London children are obese or overweight by the time they finish primary school. Several boroughs, including Barking and Islington, already have measures to control the number of takeaways near schools.

Currently, around one quarter of the UK's takeaways are located within a five-minute walk of a school, with more than 8,000 fast food outlets in London alone.

Kahn is set to announce the policy in the upcoming London Plan, an annual document which sets out how the capital will "evolve and develop" in the approaching year.

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."

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."

Elsewhere, Kahn will also announce plans to protect the "lungs of the capital's" Green Belt and to make London more than 50% green by 2050 as well as increasing the target number of homes built every year in London from 29,000 to 66,000.

Khan said: "London needs 66,000 new homes every year to meet its increasing need and put right years of underinvestment. But development must not be done at any cost: the Green Belt is the lungs of the capital and must be protected.

"Since I took office I have refused a number of developments which would have caused harm to the Green Belt. With my new London Plan I'm sending a clear message to developers that building on or near the Green Belt must respect and protect this vital natural resource."

Sadiq Khan
London Mayor Sadiq Khan has strengthened the commitment to protect the London's Green Belt REUTERS/Neil Hall