Rowers are asking Thames Water to step-up efforts to protect river users and river ecology after 920,000 tonnes of raw sewage was dumped in the Thames earlier this month.

The sewage was pumped from Thames Water’s plants at Mogden, Crossness and Beckton, but because Mogden is in Isleworth sewage flows downstream through Wandsworth.

Thames Water legally releases sewage into the river, but this huge release caused more than 200 fish, mainly flounder, to die - as well as leaving formations of faeces floating around the river.

Anatole Beams, safety advisor for the Amateur Rowing Association, said the problem was not new.

“There was a big release in 2004 but this one is terrible. In the past we have had stomach bugs, eye infections and we even had one case of blood poisoning. New rowers are also prone to getting ill.”

Mr Beams is due to meet with TW officials shortly to discuss the problem.

A spokeswoman from Thames Water said planned expansion would reduce the need for it to use storm tanks on the site preventing untreated water from spilling into the river.

He said: “The discharges over the past week draw into sharp focus the need for us to significantly boost treatment capacity at Beckton, Crossness and Mogden sewage works and to begin work on the proposed London Tideway Tunnels - work to help clean up the Thames by reducing the amount of storm sewage over-flows.

“Until this essential work is done, London's sewer network - which is Victorian - and other facilities will remain overstretched. This means that after heavy rain there is simply nowhere else for excess storm sewage to go, which is why these discharges, though regrettable, are legal and consented.”

In 2004 hundreds of fish were killed when one million tonnes of sewage was pumped into the Thames after heavy storms.

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