In a move highlighting the speed with which accusations of "greenwashing" can force firms to change their environmental policies, coffee chain Starbucks has announced it is actively investigating alternatives to its practice of leaving taps running all day in its stores – just 24 hours after a tabloid investigation exposed its wasteful water practices.

A story in The Sun newspaper claimed the chain's utensil cleaning "dipper" system wastes 23.4 million litres of water – enough to fill an Olympic swimming pool every 83 minutes – by being left on all day.

Starbucks initially told The Sun that its system used less water than turning taps on and off again. However, the company then said in a statement that the taps needed to run all day for hygiene purposes.

But both claims were rubbished by environmental and waste campaigners.

"The claim that you need to keep taps running non-stop for health and safety reasons is bonkers," said Peter Robinson, director of environmental charity Waste Watch.

Pressure on the firm grew as the Guardian and the BBC Ten O'Clock News both picked up on the story.

It also prompted a response from the minister for environment, food and rural affairs Hilary Benn, who said that "big companies must show leadership" and not waste water.

A day on, the media furore appears to have forced Starbucks into a change of position, with the company releasing a fresh statement, claiming it is "working as a priority on alternative solutions".

It added: "We recognise the opportunity exists to reduce our water usage."

The coffee chain said it was currently testing a new system using dishwasher s to clean service utensils as well as designing a more efficient spoon rinse.

And it will work closely with UK NGO Waterwise to reduce waste.

"In the short term Starbucks could look at ways of reducing flow rates and at finding times when the tap can be turned off and these two simple approaches should be able to roughly cut wastage in two," said Jacob Tompkins, director of Waterwise.