The empty building in Brixton has become a popular spot for the women to offer their services to customers, The Sun reports.
A local resident said: "It's disgusting. This area used to be quite nice, but the tone is being lowered."
Police said they were aware of concerns about the empty Jobcentre, which closed down this summer.
In other prostitute news, a German ice hockey team recently attracted controversy after being sponsored by a local brothel.
Team spokesman Jürgen Eichbauer defended the move, saying: "The operators of the brothel are legal people who do their business honestly and pay taxes.
"No Wild-West methods are used, and the women are not forced. Prostitution is the oldest business in the world and therefore the cooperation is not objectionable to us."
> Car wash offers free sex to customers