Tap water provided by Thames Water is the best in its class, according to the Government's official quality control watchdog.

The Drinking Water Inspectorate, announcing its annual water quality report, said that in 2008, Thames Water’s tap water was 99.99 per cent compliant with national and European standards – the company’s best-ever performance.

This means that, for the second year running, the quality of Thames tap water is better than all of the other large water and sewerage companies in England and Wales.

David Owens, chief executive of Thames Water, said: “Substantial investment to improve drinking-water quality, funded by customers’ bills, is paying off.

“This is reflected in our outstanding results. We plan to continue our investment programme.”