Sadiq Khan has told Lewisham Council an application for 393 flats in Deptford with only 10 per cent affordable housing goes against London-wide planning regulations.

The proposals would see a five, 26 and 30-storey building with 393 one, two and three-bed apartments, retail and office floorspace, and an extension to the Trinity Laban Conservatoire of Music and Dance on the derelict site in Copperas Street.

The Mayor of London’s report outlined that while redevelopment of the site was supported, the affordable housing offer was unacceptable and did not comply with the London Plan.

“The offer of 10 per cent, made up of 100 per cent shared ownership, is wholly unacceptable,” the report explains.

Officers wrote the level of affordable housing could be “significantly increased” because a third of the site is in public ownership.

The proposals also include new educational facilities for Trinity Laban which would contribute land for a fifth of the site.

But officers were concerned the costs of the new facilities weren’t clear.

“This all supports a significantly increased level of affordable housing, together with a greater diversity of affordable tenures. The financial viability assessment does not include costs for the fit-out of the Trinity

Laban facilities, which raises concerns that the organisation is not receiving a benefit commensurate with its land contribution, and that the facilities may be delayed due to insufficient funds,” the report adds.

The application also does not comply with London Plan and draft London Plan policies on energy, flood risk, sustainable drainage, and water infrastructure, according to the report.

Daylight levels were also a cause for concern, as well as the impact on Maritime Greenwich World Heritage Site.

The London Mayor is consulted on all planning applications that are of potential strategic importance in London.

Once a council has decided to refuse or grant planning permission to an application of potential strategic importance, he can allow the decision to stand, direct refusal or take over the application.