E.coli has been traced in multiple water samples from the stretch of the River Thames that will host the famous Boat Race on Sunday, campaigners say.
Campaign group River Action, which started testing for the bacteria in the Thames on 10 March, said almost a third of samples (29.5%) exceeded safe limits for entering the water.
Water quality would be classed “poor” by official standards if it were a bathing water site, according to the campaigners.
In response, Thames Water said rivers were “very dynamic environments” and recent tests on E.coli carried out by Fulham Reach Boat Club had shown results “within the ‘excellent’ threshold since the start of March”.
The Boat Race between Oxford and Cambridge Universities in London traditionally culminates in the winning team throwing their cox in the water, but last year they were warned to avoid the water after “alarmingly high” levels of E.coli were found.
Five-time Olympic gold medal-winning rower Sir Steve Redgrave said rowers and others who enjoy the water “deserve better”.
“It’s a real worry that in 2025, unsafe water quality in the Thames is still a concern,” he added.
Last year, an Oxford rower said he had fallen sick from E.coli after training on the Thames and spotting “poo in the water”.
Thames Water said the boat race route was not technically bathing water, meaning it is not funded to routinely disinfect or sterilise the water in the same way.
Britain’s biggest water supplier has been battling against financial collapse since last year, narrowly avoiding being taken into government ownership last month.
How was the testing carried out?
The stretch of water on the boat race route is not classed as a bathing water site by the Environment Agency, but the campaigners said they measured it in the same way in a bid to highlight the levels of water pollution.
River Action said it sampled water 44 times between 10 March and 7 April, from three different locations along the race route.
The group said the percentage of samples which exceeded safe limits for entering the water was almost three times the threshold for bathing waters rated “poor”.
River Action’s Erica Popplewell branded it “a scandal” and called for Thames Water to be put into government hands.
“We strongly suggest that the winning team on Sunday think twice before throwing their cox in the Thames,” she added.
The levels of E.coli were found in spite of the recent dry weather, the group said.
Untreated sewage is only supposed to be released from emergency overflow valves during exceptionally wet conditions, to avoid sewage backing up into people’s homes.
A Thames Water spokesperson said: “Rivers are very dynamic environments, and samples can vary hugely within a short period of time. Paradoxically, recent tests on E.coli carried out by Fulham Reach Boat Club have results within the ‘excellent’ threshold since the start of March.”
The spokesperson added: “We have and continue to deliver a record amount of investment to address our ageing infrastructure and the health of rivers. This includes £1.8bn to improve river health in London over the next five years.
“We are committed to seeing waterways thrive, but we can’t do it alone. E.coli can come from a variety of sources including animal faeces, agricultural waste, road run off and sewage.”