Labour’s London mayoral hopeful Diane Abbott yesterday called for a system of private-sector rent controls.

She said that monthly rents should be no more than 50 per cent of the local annual council tax bill, in a paper published by campaign group Generation Rent.

Landlords would be able to opt out of this proposed rent control system by agreeing to a surcharge on the rent they receive above the cap.

The money raised would go to the Mayor of London fund for new social housing in order to reduce housing demand and lower market rents.

“A major international city without measures to stabilise rent runs the risk of rents spiralling out of people’s reach,” Ms Abbott said.

“It is no coincidence that New York, Paris and Berlin all have some version of rent control.”

Official figures from 2013-14 have shown the median cost of private rent in London is more than half of a Londoner’s median salary.