Sir Sadiq Khan is on course to miss the government's recently reduced affordable homes target for London by a wide margin, new City Hall figures show.
Fewer than 8,000 homes have been started under the 2021-26 programme, leaving the mayor needing almost 10,000 more in the final three months to hit the lowered goal.
Overall, London has achieved only 41-44% of the revised Affordable Homes Programme (AHP) target, figures show.
City Hall Conservatives branded the record a "failure", while City Hall said housing starts had risen sharply despite "challenging economic conditions".
In October, the Greater London Authority (GLA) and Ministry of Housing, Communities and Local Government (MHCLG) agreed to lower London's target for the Affordable Homes Programme (AHP) for 2021-2026 by more than a fifth to between 17,800 and 19,000 starts by March.
Since the programme was signed off in July 2023, 7,878 homes have been started up to December 2025 - 5,188 in the first 21 months and 2,690 since.
Unless 9,922 additional starts are delivered between January and March, the mayor will fall short of the target.
A City Hall source said housing starts in the 2021-26 AHP had more than doubled compared with the same period last year, from 1,249 to 2,690, and that council home starts had increased nearly five‑fold, from 228 to 1,371.
The mayor has come under heavy criticism in the past for his record on housebuilding.
Both Sir Sadiq and his deputy mayor for housing Tom Copley have blamed high interest rates, rising construction costs and delays linked to the Building Safety Regulator (BSR).
City Hall says it is taking steps to boost delivery, including slashing affordability quotas and launching a multi‑billion‑pound fund offering developers 0.1% interest loans.
However, City Hall Conservatives' housing spokesperson, Lord Bailey, said ministers should intervene, calling the figures "a failure".
"Under Sadiq Khan, just 1,898 homes have been completed from the £4bn 2021-26 programme in a city of nearly 10 million people," he told the Local Democracy Reporting Service (LDRS).
"Fewer than 8,000 homes have even been started, against an original target of 35,000, and still far short of the already reduced expectations for March." He added: "This is not just a statistical embarrassment; it is a human crisis." "Families are stuck in overcrowded homes; councils are buckling under soaring temporary accommodation costs; rents continue to climb; young Londoners are locked out of home ownership."
A spokesperson for the mayor told LDRS tackling the housing crisis remained a "top priority".
"Housing starts have significantly increased compared to this time last year, alongside council housing starts," they said.
City Hall said the mayor focused on social rent homes despite tough conditions, leading to the highest council house completions through GLA funding since 2016-17.
The spokesperson said since 2018, 25,000 council homes had been built "or are being built" with City Hall funding.
"These achievements come despite tough economic conditions," the spokesperson said, citing the "disastrous legacy of the previous government", high interest rates, rising construction material costs, Brexit, pandemic effects and Building Safety Regulator delays.