THAMES WATER plans to spend £1 billion replacing more than 1,000 miles of crumbling Victorian water mains in Central London over the next five years.

The water company said that mains replacement was the top priority in the capital, if London’s water supply was not to be jeopardised.

The urgency of the massive project has been underlined by last year’s exceptionally dry summer and by forecasts that London’s population is set to grow rapidly.

Inner London boroughs, including Islington, Camden, Westminster, Hammersmith & Fulham, Kensington & Chelsea and Tower Hamlets, urgently need leaking water mains replaced.

A third of the water mains network in the capital is more than 150 years old and more than half is over 100 years old.

John Sexton, managing director of Thames Water, which is owned by RWE, the German utility giant, said that the company wanted to replace six times more water mains than it has in the past five years. Neglecting this work could place London’s water supply at risk, he said.

Mr Sexton urged ministers to consider that RWE’s shareholders alone could not fund such a huge programme of work.

In previous years Thames has had to devote most of the £6 billion investment programme allowed by the water regulator to environmental improvements, including the quality of waste water returned to rivers.

Thames Water has one of the worst records in the country for leaks, as the capital’s infrastructure is the oldest in the country and is built on clay. From 1996 to 1999 leakage was reduced by about a third, but extreme weather conditions, including heavy autumn rainfall and last summer’s prolonged dry spell have further damaged the ageing pipes. The corrosive nature of clay soils in inner London also damages water mains, as does the capital’s 24-hour traffic.

A pilot mains-replacement programme, begun in Bethnal Green in 2002, has been extended to 11 other areas and another ten areas are under development for 2004.

By the end of March Thames Water will have spent £53 million on the project, replacing 68 miles of mains.

Thames has promised to minimise disruption to the capital during the replacement programme by working closely with other utility companies, local highways authorities and Transport for London.