Starbucks was blasted by environmental experts Sunday night after The Sun discovered it pours millions of gallons of precious water down the drain at its coffee shops.

The giant coffee chain has a policy of keeping a tap running non-stop at all its 10,000 outlets worldwide, wasting 6.2 million gallons a day.

That would provide enough daily water for the entire two million-strong population of drought-hit Namibia in Africa, or fill an Olympic-sized pool every 83 minutes.

Every Starbucks branch has a cold tap behind the counter providing water for a sink called a "dipper well," used for washing spoons and utensils.

Staff are banned from turning the water off under bizarre health and safety rules -- bosses claim a constant flow stops germs breeding in the taps.

Starbucks has built up a massive chain, popular with coffee drinkers from Hollywood stars to construction workers, and proudly boasts of its work for the environment.

But water companies accused the firm of harming the environment by frittering away a vital natural resource.

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