The London Plan contains provisions which allow developers to charge up to 80% of market rent for affordable homes. Under the Mayor's early minor alterations to the Plan, which were approved by the London Assembly in September, boroughs within the capital are prevented from setting individual rent caps or targets for affordable rented homes in their local development frameworks.
Southwark Council, which sets its social rent at around 40% of market values, said it had launched the challenge "in order to achieve affordable rental levels for residents".
"We have challenged the Mayor's decision because this is a vitally important issue for an inner-London borough like Southwark," said the Council's cabinet member for regeneration and planning Fiona Colley in a statement. "Councils need every power possible to ensure rent levels are appropriate and affordable for their residents."
"Maybe there are some areas of London where rent levels of 80% of market rent are affordable to most people, but they certainly aren't in Southwark. The implication of the Mayor's decision is that councils will have little power to make sure new affordable housing is really, genuinely affordable for local people," Colley said.
The Council said it expected a hearing on its application to take place in the spring 2014.
