BusinessHousebuilders fight Sadiq Khan on retirement homes planCompanies such as McCarthy & Stone build retirement homes for older BritsAFP/Getty ImagesJoanna Hodgson17 November 2017A group of housebuilders on Friday warned spending on homes for the elderly could dry up as they launched legal action over Sadiq Khan’s affordable housing plan.The retirement builders, including FTSE 250 builder McCarthy & Stone, are concerned about the Mayor of London’s decision to offer developers a fast-track route through the planning system if they provide 35% affordable housing on site.They are worried that the nature of specialist housing for the elderly, which could include ramps and healthcare facilities, means it is more expensive to create than traditional homes. Therefore on-site affordable housing is not always feasible.Under the latest supplementary planning guidance, the builders allege they would be placed on a slower planning path.McCarthy, Churchill Retirement Living, Renaissance Retirement and PegasusLife have filed a claim for a judicial review of the decision by Khan to issue the SPG this year.Read MoreWH Smith hire turnaround veteran with package that could be worth £25mBlue Posts boss: If opening a pub becomes so risky, people just won't do itCulpeper pub boss: Rates system is not fit for purpose — and not fairSponsoredReset your wellbeing for the year aheadThe firms said: “Few if any new retirement sites will come forward under the Mayor’s new SPG.”Property Week magazine said the legal challenge has been made on grounds including that the guidance should have undergone an independent examination.City Hall said the guidance was consulted on for three months and it will respond to the claim.MORE ABOUTMcCarthy & Stone