An area of Streatham Park has been closed off due to a defective wall.
Residents of Hillside Gardens, Streatham Hill, can’t access part of the park which is designated as a informal play area.
Hillside Gardens, which is run by the council’s housing firm Lambeth Living (LL), recently celebrated winning a second Green Flag award.
The wall in question shields users from derelict garages and a bank of earth.
Liberal Democrat councillor Jeremy Clyne, said during a full council meeting on June 20 Labour councillors voted against urgent action being taken.
He said: "It is shocking that the council and LL have failed to deal with this danger to park users and appalling that Labour councillors should vote on party lines to stop action being taken."
A LL spokesman said: "We are aware that this wall needs repairing and we are exploring all possible funding options for the works".