London councils launch legal challenge against Mayor over affordable housing targets

On Wednesday, Tower Hamlets, Hackney and Lewisham councils filed a legal challenge to the High Court over the Mayor of London’s plans to cut the affordable housing quota by 15%. 

The councils allege the Mayor of London Sadiq Khan has attempted to reduce the current 35% housing quota to 20% without using the proper statutory process for amending his previous plan, and without offering evidence to justify the blanket reduction across all London boroughs.

The legal challenge sees Tower Hamlets, controlled by the Aspire party, collaborating with the Greens in order to put pressure on City Hall. 

The coalition submitted a judicial review claim to the Greater London Authority, raising concerns about the impact the policy may have on the ability of councils to deliver the higher levels of affordable housing for residents. 

Four additional councils, Lambeth, Southwark, Waltham Forest and Haringey are formally supporting the challenge. Lambeth, Waltham Forest and Haringey have a majority of Green councillors, after a historic surge in the party’s vote share in the capital during the May 2026 Council Elections. Southwark gained 22 Green councillors, narrowing their historic Labour majority to 7. 

 

In October 2025, the London Mayor lowered the affordable housing target from 35% to 20%. The move was another step back from his initial 2016 target, set at 50% of all new homes in London. Local authorities, MPs and housing organisations like Shelter and the National Housing Federation previously criticised the lower target with fears that it would deepen housing inequality and homelessness as waiting lists soar.  

The newest target slash was first announced in October 2025 by the Housing Secretary Steve Reed as an “emergency” intervention, which Khan approved, with the stated aim that dropping the targets would help unlock the London housing market and incentivise developers to pursue more projects at a time when housebuilding had stagnated. 

Khan has previously defended lowering the affordable home targets, arguing that housebuilding was facing a “perfect storm” caused by high interest rates, Brexit, rising construction material costs and pandemic aftershocks, calling it the most “difficult period for housebuilding since the global financial crash.”

Proposed developments at the 20% affordability mark will now qualify for the Mayor’s fast-track planning application. Schemes starting before 2030 will also be offered temporary relief from paying the Community Infrastructure Levy (CIL). CIL payments are used to fund infrastructure such as the construction of the Elizabeth Line. 

Several developers and architects voiced their support for the lowering of the target on LinkedIn, given the current viability crunch. Chris Fellner, Director at Haworth Tomkins writes, “Speak to any architect, developer or local authority housing officer and they are all desperate for things to move forward. Even though I would love to deliver even more affordable homes, the emergency measures introduced by the GLA have been a first welcome step in the right direction. 20% of something is better than 35% of nothing.”

 

Others called for an end to the “cross-subsidy model” which relies on the private sector to build affordable homes. “Perhaps the cross-subsidy approach should just be declared dead,” commented Angela Koch, Director of ImaginePlaces. “The focus should be on public investment into public infrastructure including affordable housing.”

However the council coalition, which have committed to increased powers for local authorities to spur on housebuilding in their manifesto, are concerned that a reduction in affordable properties entering into the market will only worsen the London housing crisis. 

 

“The Mayor of London is no longer surrounded by councils willing to sign off any developer-driven decision he wants to make. Hackney now has a Mayor who will go to bat for affordable housing” stressed Mayor of Hackney Zoë Garbett.