Children are playing yards from sewage spewing out next to a popular park due to a leaking drain.
Waste has been pouring from a manhole cover in Poulters Park for the past two years and nothing has been done about it, according to residents.
Antony Knowles, 71, of Peterborough Road, Carshalton, said the smell is "absolutely atrocious", despite numerous phone calls to Sutton Council.
He said: "I walk my dog up there on a morning, and the smell is horrific. There are kids playing in the park and they are not far from this sewage.
"If their football came over the fence they would have to retrieve it from who knows what.
"When I complain to the council I get fobbed off, something needs to be done."
Mr Knowles thinks some of the sewage could be running down from Mitcham Rugby Club, which is based at the park on the border of Mitcham and Carshalton.
He said: "Wherever it is coming from it needs to be stopped, its not just in one place, its seems to be next to stile, around the paths.
"Its disgusting, this is supposed to a park not a swamp."
Councillor Jill Whitehead, chairwoman of the environment and neighbourhood committee, said: "We are very aware of this ongoing problem.
"We apologise for any issues this has caused and are taking the appropriate action.
"The sewer has been cleared out regularly as a temporary measure and the surrounding area has been cleaned up.
"This week (Thursday March 13) we will be installing more powerful new pumps which are fitted with macerators and biological filters.
"These new pumps should be capable of dealing with the issue and ensuring it does not recur."