Sewage is covering the towpath at a tourist canal spot, making boaters feel "sick" from the stench.
The National Bargee Travellers Association (NBTA) says untreated sewage overflowing from damaged facilities at Little Venice has been seeping over towpaths and into waterways for more than a week, causing businesses, boaters and tourists to suffer.
The group, which campaigns for travelling boat dwellers, has hit out at the Canal & River Trust, which runs the facilities, accusing the charity of "negligence".
A visiting boater, who asked not to be named, said the waste disposal point was unusable.
He said: “I pulled over to use the facilities and was so bowled over by the smell of rotting faeces, I ran back to my boat to vomit.
"There was excrement under the water taps.”
A permanent resident on a Canal and River Trust mooring said: “I am selling my boat but, before a recent viewing, the toxic smell of sewage caused me to be sick multiple times.
"I called but they just put tape around it.”
The NBTA said since the CRT took over management of 2,000 miles of waterways in 2012, it has built no new sewage disposal points or waste facilities during its tenure despite a 15% rise of liveaboard boaters during the period 2011 to 2021.
Marcus Trower, chair of the London branch of NBTA said: “CRT mismanagement is putting boaters’ and the public's health at risk.
"They must immediately rectify the situation and restore sanitation facilities across the country, especially those in high-use areas in our major cities."
The CRT said boater numbers have doubled in London in the last decade, in part driven by the spiralling housing costs.
A CRT spokesperson added: “The facilities at Little Venice are among the busiest in the country and are therefore particularly vulnerable to accidental misuse and deliberate vandalism."
They said the charity spends thousands of pounds each year servicing the facilities and paying to have them fixed when they are put out of action.
They are looking at solutions to help prevent the repeated misuse at Little Venice from disrupting services for those living afloat.
The group says the cost of looking after the canals, some more than 200 years old, continues to rise.
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