Thames Water has announced plans to seek planning permission to increase the capacity at Mogden Sewage works by more than 50 per cent as part of a £400 million programme to boost water quality in the River Thames.

Currently when there is heavy rain the plant cannot cope with the extra rainwater and sewage and this can result in sewage diluted with rainwater being discharged into the river, to prevent flooding.

Investment at the site, which serves Twickenham residents and the surrounding areas, will increase the volume of water that can be treated at Mogden and reduce the frequency of discharges into the Thames.

Nick Facett, Thames Water's Project Manager said; "We're committed to a massive programme of investment across all our London sewage treatment works with the objective of improving the environmental quality of the River Thames."

He said Thames Water would be holding public meetings before submitting a planning application to Hounslow Council so that residents can find out more about the proposals and make comments.

"We want them to have their say," he said Mogden Residents Action Group (MRAG) who attended a recent meeting of the Thames Water Mogden Liaison Meeting said the "massive expansion" was being rushed through.

Trevor Whittall chairman of MRAG said before any proposals for the expansion of Mogden are considered, residents want the Odour Improvement Plan finished and evaluated.

He said: "MRAG is not opposed in principle to the expansion of the capacity to deal with flooding as it should reduce the use of storm tanks but we want a delay on construction until 2009 not only to ensure that the Odour Improvement Programme has worked but to ensure residents around the plant do not suffer undue disruption. Also we want assurances the catchment area will not be enlarged and that the remaining storm tanks will be enclosed."

At a presentation by Thames Water to the Brentford and Isleworth Monitoring group Councillor Phil Andrews asked: "Thames Water has not been a good neighbour. It has not committed a penny from its own resources to ease the suffering of the surrounding community, in spite of the fact that it has both the technology and the financial resources to do so.

"As the elected representatives of your victims, could you please explain to me why you would expect us to look sympathetically upon your application to expand your operation still further?"

He added: "If residents do not want to see Isleworth, Twickenham and surrounding areas turned into Europe's biggest cesspool at the expense of the local communities whilst increasing the profits of Thames Water shareholders, we urge them to offer their elected councillors every possible support on this issue which could affect the community for decades to come."