The probe into Camden Council by the Regulator of Social Housing came after it was fined £500,000 over a fatal fire in Hampstead in November 2017.
The investigation found that over 9,000 fire remedial actions are currently overdue, just under 400 of which were deemed “high-risk”.
A third of the fire safety jobs should have been completed within 10 days and the remainder in 30 days.
As part of the probe, the regulator obtained a 2019 audit of fire safety from Camden, which found there were over 6,000 overdue fire remedial actions at the time.
The council was also criticised for a “potential breach" of housing standards by not having at least one smoke alarm fitted on each storey with living accommodation.
The report found: “Taking into account the outcome of the fire in 2017, the findings of the internal audit in 2019 and the current fire safety position, the evidence demonstrates a longstanding failure by London Borough of Camden to complete all fire safety remedial actions in a timely manner, and to mitigate the risks to tenants in the meantime.
“As a consequence, tenants have been, and continue to be, exposed to potential harm."
The regulator’s Kate Dodsworth said: “Camden Council has failed to address thousands of fire safety actions in its tenants’ homes.
“This is unacceptable and has put tenants at potential risk of harm.
“The council needs to act urgently to put things right, and we will scrutinise it closely as it does this."
In comments reported by the BBC, Georgia Gould, leader of Camden Council, said: “There is nothing more important than the safety of our residents and we are taking this notice very seriously."
She said a programme of work was in place for this year and next and that the council would not “be content until every action is complete”.
