The mayor of London will introduce planning regulations to protect the green belt and incorporate into new developments more 'green roofs', green walls, 'rain gardens' and habitats for wildlife.
Mr Khan will also fund thousands more trees and drive through improvements to community green spaces.
As a first step, the mayor has announced a new £9m Greener City Fund for London, aimed at creating and improving green spaces.
Local groups can apply for the first £1m of grants to plant neighbourhood trees and maintain green community areas.
The mayor of London said: “London is home to outstanding green spaces that I want to protect, invest in and improve as we aim to become the world’s first National Park City.
"We can also increase the amount of greenery in the city by installing many more green roofs and making our streets greener.
“From our famous Royal Parks, to our much-loved community gardens and urban nature reserves like Woodberry Wetlands, this ‘green infrastructure’ is a vital asset that improves air quality, boosts quality of life, conserves wildlife and attracts thousands of visitors.
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“I’ve set out my plans to improve London’s environment by fighting pollution, tackling waste and promoting cleaner energy so we can make London a healthier city that adapts to the impacts of climate change.
“I want to hear your views and ideas about how we can make London the greenest city in the world.”
Mr Khan made the announcement at the launch of his draft Environment Strategy for consultation at Woodberry Wetlands in Hackney, alongside the London Wildlife Trust.
The draft London Environment Strategy includes:
• introducing the T-charge from October this year (whereby vehicles in central London will need to meet minimum exhaust emission standards, or pay a daily £10 emissions surcharge) an ultra-low emission zone (ULEZ) in 2019 and the cleaning up of the bus fleet
• London’s first solar action plan to more than double London’s solar energy generation capacity by 2030 with measures such as a new community energy grant scheme and a ‘reverse’ solar auction
• a new fuel poverty action plan to increase support for those struggling to heat and power their homes through a £10m energy efficiency delivery programmes, referral services and programmes that provide direct advice and support to the fuel poor and support to improve enforcement action against landlords who do not meet legal requirements
• policies to encourage better use of resources, including setting minimum recycling standards and help cut food waste by 20% per person by 2025.