The National Trust is calling for 600 new “street parks”, filled with fruit trees, to be created in the “grey deserts” of Britain’s cities.

The plans propose converting side streets into green oasis for neighbourhoods more than 800m from an existing park.

While the scheme would cost £400m, the National Trust estimates it would deliver health and wellbeing benefits worth £100m a year.

The trust also called for a wider £5.5bn programme to upgrade the country’s existing parks.