Starbucks says it is balancing water conservation and customer safety
US coffee-shop chain Starbucks has defended itself against claims of a serious waste of water by leaving taps running in its stores all day.
A spokeswoman said the purpose was to clean utensils and the policy meant the company met health standards.
But environmental groups have criticised the practice, accusing Starbucks of wasting millions of litres of water every day.
Campaigners say the firm should look at more water-efficient ways of cleaning.
A report in the UK's Sun newspaper said the cold taps are left running in thousands of Starbucks branches around the world every day.
The company says the flow services a "dipper well", used for keeping utensils clean, and that the taps run at very low pressure.
"Dipper wells use a stream of continuous cold fresh-running water to rinse away food residue, help keep utensils clean and prevent bacterial growth," the Press Association news agency quoted the spokeswoman as saying.
"The dipper well system currently in use in Starbucks retail stores ensures that we meet or exceed our own and local health standards."
She said the company was considering using dishwashers instead of the dipper wells and introducing a more water-efficient way of cleaning spoons.
Starbucks says although it recognises that there are opportunities to reduce its water usage, it does comply with United Nations standards, and it has to balance water conservation with the need for customer safety.
But environmental groups said they were shocked at what they said was serious water wasteage.
"I think it is fair to say that Starbucks have a good environmental record, as far as we understand it, and so we are mystified by this story," Barrie Clarke, of Water UK, told PA.
"We think that it sounds like a serious waste of water and an unnecessary waste of water because we are at a loss to know what that purpose of it is."
"There must be other ways of ensuring hygiene in a coffee shop other than allowing a tap to run all day long," Barrie Clarke added.