Leakage by water companies across England and Wales has increased to more than three billion litres every day, figures show.
Overall leakage levels have increased by 1.2% on the previous year amid concerns that the rising figure will discourage consumers from using water more efficiently, according to the annual report from the Consumer Council for Water (CCWater).
Some companies managed to cut their leakage, with the largest reductions achieved by Affinity Water, down 4.4%, United Utilities (2.8%), Bournemouth Water (2.6%) and Welsh Water (2.5%).
In contrast, Dee Valley Water reported the biggest increase, up 14.1%, followed by Essex and Suffolk Water (9.1%), Cambridge Water (8.2%), Portsmouth Water (7.6%), Thames Water (5.4%) and Bristol Water (5%).
Meanwhile, the average person still used 141 litres per day in 2016/17, up almost 1% on the previous year.
CCWater chief executive Tony Smith said: “Consumers view leakage as a dreadful waste and it can drain their own motivation to save water.
“Some water companies need to show much more ambition in tackling leaks, otherwise all of our efforts to encourage consumers to use water more wisely will fall on deaf ears.”
CCWater said it supported new proposals by regulator Ofwat for companies to reduce leakage by at least 15% between 2020 and 2025, but said it should be part of a longer-term strategy to drive down levels even further.
It said companies could achieve this by adopting new leak-detection technology and “more innovative ways of working”.
Consumers can compare how their water company is performing on a wide range of services by visiting discoverwater.co.uk.
A spokesman for Water UK, which represents water companies, said: “Leakage is an important issue, which is why water companies spend millions of pounds each year, which has helped to cut leaks by a third since the mid-1990s, and most companies are still beating their targets.
“We’ve had some major successes in combating leakage over the years, and at the same time we know that people want to do the right thing and use water wisely to help the environment.
“We all need to work together in different ways to reduce the pressure on water supplies, and that’s what water companies are doing every day.”