Councils in eight of London's 32 boroughs have failed to prosecute even a single landlord for providing unsafe accommodation during the 2015-16 financial year.
The findings have come in research using the Freedom of Information Act and conducted by the Liberal Democrat party in London.
The party claims that government funding cuts to local councils have resulted in a threadbare patchwork of enforcement against rogue landlords.
The research also discovered that half of the councils prosecuted fewer than 10 landlords for providing unsafe accommodation in 2015/2016 and that one local authority alone - Newham - was responsible for 70 per cent of prosecutions of landlords in the capital.
There was found to be significant variation in the level of enforcement activity by London boroughs, ranging from 1 in 10 private rented properties being inspected for hazards by one council, while others were only inspecting one in five hundred or even six hundred properties.