Sir Sadiq Khan has demanded councils be given powers to more than double council tax on properties sitting empty to free them up in the capital. The Mayor of London told LBC: "I'm not being funny, if you can afford a flat and leave it empty, you can afford double council tax."

The Labour mayor pointed to flats in Nine Elms, south-west London, as an example of properties "built like gold bricks investment". He said: "They've not been lived in, because those who bought it know equity will go up and the price of the flat will go up, and they don't need to live there."

He went on: "Wandsworth, great council, the max they can charge is double council tax. I am not being funny, if you can afford a flat and leave it empty, you can pay double council tax.

"I think boroughs should be allowed to charge much, much more. We're lobbying the Government to give councils more powers to dis-incentivise leaving a property empty."

This comes as the three-term mayor revealed he was "actively exploring" using green belt land to solve the capital's housing crisis.

"We have young professionals stuck in their childhood bedrooms for years on end, lifelong residents being priced out of their own neighbourhoods... primary schools closing because young families can't afford local properties," he said last week.

"The damage the housing crisis causing is pervasive and profound."