Levels of E-Coli in the Thames have been found to be 27 times the acceptable quality – just days before the Henley international regatta.
Elite rowers at the event have been advised to take precautions after a campaign group tested the water quality in the Henley mile where the race will take place.
But Thames Water accused the River Action group of being alarmist – insisting they had carried out their own tests which had given “reassuring” results.