Thames Water's chief executive has branded her own company’s performance as “unacceptable” while taking questions from MPs.

The Environmental Committee quizzed bosses from five of the largest water and sewerage companies in England on the issue of river contamination.

It follows the committee’s inquiry into water quality in rivers, which heard reports of water companies discharging raw sewage into rivers in England more than 400,000 times last year.

The Thames has been badly impacted by wastewater, with millions of tonnes of raw sewage entering the river each year.

Under questioning from EAC chairman Philip Dunne MP, Thames Water chief executive Sarah Bentley said: “Thames (Water’s) performance is unacceptable, our customers find it unacceptable to contact us.

“Our ageing infrastructure, whether that’s on the water side with leakage, or on the sewage network in terms of the capacity we are treating, needs addressing.”

Ms Bentley said that the company has a “broad range” of performance metrics that “need to change”.

“Since I joined 12 months ago I have been accelerating the money that we have got during this regulatory period”, she said.

“When I started I went out, I listened to our customers, I listened to environmental groups and members of this House, and of this committee, and it is clear that we have a broad range of performance metrics that we need to change”.

She said her company was spending £1.2billion over the next five years on improving its overall network to treat sewage and rain.

“I can understand why people are genuinely upset and concerned about the quality of the rivers and the situation with sewage discharge into those rivers,” she said.

“A number of my colleagues have suggested making sure that we transparently share information about when those spills are occurring.

“More importantly, what I have heard in the year that I have been running Thames is that our customers just find spills unacceptable, and we find them unacceptable and I’m really committed to finding out how we can eliminate storm discharges so that people can swim confidently in the river.”

Previously the EAC heard that just 14 per cent of English rivers are currently rated an ecological status of ‘Good’, and that not one river in the country is rated ‘Good’ on its chemical status.

In a statement the EAC said that one of the main sources for this is sewage discharge from the water industry.