London Councils has released new analysis warning that boroughs need to make over £500m of savings next year to balance their budgets.
Nine in ten London boroughs expect to overspend on their budgets this year - estimated at over £400m in total across the capital.
Cllr Claire Holland, Acting Chair of London Councils, said: "Borough finances are on a knife edge - with grim implications for the future of local services in the capital."
"The combination of higher costs due to spiralling inflation, skyrocketing demand for services, and insufficient levels of government funding leaves boroughs in an extremely precarious position."
Ahead of the government's Autumn Statement in November, London Councils has launched its key priorities. These include an overall funding increase of at least 9 per cent, investment to reduce homelessness, and reforms to the broken local government finance system.