Residents in Glenrothes have complained about the stench from Stenton pond, which has turned green with raw sewage.
Once a beauty spot, one man who lives metres from the pond has said it has become a nightmare.
One local described the pond online as smelling “like death”, with local wildlife swimming around in the murky green water.
Swans and ducks could be seen in the water in Glenrothes on Tuesday, with one swan’s nest surrounded by the sewage.
Glenrothes resident Alan Mowbray said he has contacted Scottish Environment Protection Agency (Sepa) without success.
Alan said the issue began in February and he initially thought the smell was caused by blocked drains in his street.
Concerned about the impact on the wildlife, Alan even considered calling Police Scotland’s wildlife team.
“It’s horrible, I’ve never seen anything like it,” Alan said.
“It’s just raw sewage, you can even see where it has dyed the metal white – that’s what raw sewage does. It smells of sewage.
“I wonder what it is doing to the animals.”
Alan said he had been unable to find exactly where the contamination had come from.
Reeds at the side of the pond, seen as important for biodiversity, are now visibly clogged with sewage.
The pond was hit by an oil spill in 2014, which left a swan with diesel burns, with the SSPCA urging locals to dispose of fuels responsibly.
A spokeswoman for Scottish Water apologised and said work was under way in the nearby area.
She added: “We have ongoing investigations into the surface water network that discharges into Stenton Pond.
“We have carried out some sewer repair work and are also carrying out regular checks and clean-ups of the area.
“We have an outstanding sewer repair to complete that requires us to access a customer’s property and this will be done when we have the authorisation to carry out the work, which we hope will be next week.
“We will continue to monitor the network and apologise for any inconvenience caused.”
A spokesperson for Sepa said: “Sepa was made aware by a member of the public of potential sewage pollution in Stenton Pond in Glenrothes.
“We are engaging closely with Scottish Water as it investigates the network in the vicinity and if sewage is present, will ensure that a thorough clean-up is conducted.
“Anyone concerned about potential pollution incidents should contact us via our 24-hour online form at www.sepa.org.uk/report.”