Reassurance has been sent to Twickenham MP Vince Cable that work is being carried out to clean up the Thames, after 450,000 tonnes of sewage was discharged into the water.

The Environment Agency (EA) has contacted Dr Cable to reassure him that work is well under way, after heavy rainfall led to the sewage being pumped into the river on June 5, resulting in the believed death of thousands of fish.

Dr Cable said: “This should not be happening in the 21st century in one of the most developed capital cities in the world.

“I will keep track of progress being made in cleaning up the damage after this latest spill, but the sooner we have a long term solution in place the better.”

Thames Water is conducting the clean up with EA officers supervising the operation, with oxygenation vessels pumping oxygen into the water in an attempt to minimise fish deaths.

Martin Baggs, chief executive of Thames Water, apologised for the incident and said a major programme of work was being carried out to prevent the problem from happening again..

He said: “In the west London area this includes a 50 per cent increase in treatment capacity at our Mogden sewage treatment works, which will be complete early in 2013, and the proposed Thames Tunnel.”