By Paul Majendie

LONDON, July 25 (Reuters) - Prime Minister Gordon Brown said Britain must do more to boost its flood defences after the worst floods in 60 years left 350,000 people without drinking water and power supplies on the brink of mass blackout.

"We are looking at 21st century extreme weather conditions," Brown told BBC Television after a tense day monitoring how emergency services coped with the flooding that deluged huge swathes of central and western England.

Less than one month into the job as Britain's new premier, he said everything had to be looked at from infrastructure and drainage to where utilities were located to combat extreme weather conditions.

Asked if the Labour government had done enough over the past decade in office, Brown said investment in flood defences had already been doubled to 600 million pounds before the current crisis "so we are aware more has got to be done for defences."

As the political debate intensified over whether authorities could have done more, a poll from Channel 4 Television showed only eight percent blamed the government.

Twenty-five percent believed climate change was the cause while an overwhelming 61 percent called it a freak event.

One electricity switching station at Walham, near the western city of Gloucester, came perilously close to flooding with emergency services working frantically overnight to shore it up as the water came within six inches of breaching defences.

That would have left up to 500,000 people without power and plunged hospitals, stores, shops and homes into chaos.

The flooding turned the historic market town of Tewkesbury into an island where only the 12th century abbey stood unscathed on high ground at its heart. Lifeboats scudded down the main street, boats moored in car parks.

Authorities warned 350,000 people they could be without fresh water for up to two weeks. The army was called in to supply million of bottles of water as anxious families queued up for supplies and loaded them onto supermarket trollies.

While Britain struggled with floods, central and southeast Europe faced a heatwave. Up to 500 people are estimated to have died in Hungary as temperatures soared, and the heat also killed 12 Romanians.

The flood waters were receding in the worst hit areas of England but the environment agency still had six severe flood warnings in force amid fears that renewed rain forecast for later in the week could spell more trouble.

Environment Secretary Hilary Benn warned that the crisis was far from over and had "caused considerable human distress."

A teenage boy is still missing in Tewkesbury, one man died in a flooded cellar and a woman trapped in the floods lost her premature newborn twins despite being rescued by a Royal Air Force helicopter.

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