Frank Dobson, the party's environment spokesman, used the figure - amounting to one fifth of the water distributed each day in England and Wales - to attack moves to increase metering.
Claiming that the installation of metres would mean a bill of pounds 5bn for consumers, Mr Dobson said: "The Tories say that installing water meters is the best way to conserve water. That's just not true. Water meters would do absolutely nothing to stop these daily multi-million gallon leaks from the companies' pipes."
Labour's figures, not disputed by the industry, show North West Water losing 158 million gallons a day, Thames Water 138 million gallons, Severn Trent 115 million gallons and Yorkshire Water 103 million.
"Water companies up and down the country are asking people to cut down on the amount of water they use," Mr Dobson said. "Hosepipe bans have been introduced. But the real water-wasters aren't the customers, they're the water companies."
Mr Dobson said a Labour government would require companies, either through the regulator or a change in the law, to reduce the amount of water they were wasting and oblige them to help customers to reduce leaks around the home.
The industry was quick to put the leakage figures into perspective. Thames Water pointed out that it had 31,000km of mains spread over 5,000 sq miles with 18 million joints.
The company said it was investing pounds 300m in the network over five years, had the cheapest bills in England and Wales at pounds 172 a year for an average household and was not advocating compulsory metering.
For the consumer's benefit, the company also added that a tap that drips once a second wastes 10,000 gallons a year, enough for 600 baths.
Janet Langdon, director of the Water Services Association of England and Wales, which represents the 10 privatised water companies, admitted there was "a certain amount of leakage".
She said companies had spent pounds 4bn on the network over the past five years - and that only reduced leakage by 1 per cent. "We have to look to make certain we give customers the best value for money and that there is an economic level of leakage.
"To reduce leakage by a great amount would cost an enormous amount of money which would not pay off for the customers."
Ms Langdon said Britain did not suffer from a water shortage and used only 4 per cent of rainfall. Only about 2 per cent of households currently had restrictions on their water usage and that was on hosepipes and sprinklers. In the drought five years ago 40 per cent of households suffered restrictions.
Only 7 per cent of households were metered, she said, and the water companies had asked the Government for an extension of the use of rateable values beyond 2000, and for the use of council tax as a method of charging. Not surprisingly, the move to metering is strongest in the driest parts of the country, notably the Anglian area which also has one of the best records on leakage.
Hosepipe bans affect some 600,000 people in West Yorkshire, 230,000 in West Sussex and 9,000 in west Cornwall. North Surrey and Mid Southern have sprinkler bans.
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