There was a decline in sales of mineral water last year
A survey by the magazine Which? suggests many people are no longer drinking mineral water.
A quarter of people who answered the survey said they were drinking less bottled water than a year ago.
Shoppers in Britain spend £1.5bn a year on bottled water but Which? said retail figures showed a 9% drop last year.
But the British Soft Drinks Association disputed these figures, saying that people were "actually buying more bottled water than last year".
Which?'s survey also suggested half of consumers cannot differentiate between bottled and tap water and 84% of people thought tap was better for the environment.
Which? editor Neil Fowler said: "There are plenty of good reasons for choosing tap water. You can save money, it's better for the environment and it can taste just as good - if not better.
"The UK has some of the safest and best quality drinking water in the world. It's time we started appreciating it."
British Soft Drinks Association spokesman Richard Laming said: "More than 30m people in the UK choose to drink bottled water and particularly like the fact that natural mineral and spring waters have a pure, fresh taste, are naturally pure and not treated with chemicals.
"More than 75% of bottled water drunk in the UK is sourced from UK producers and the majority of the rest comes from nearby on the continent.
"Bottled water comes from fully sustainable sources and accounts for just 0.03% of the nation's carbon footprint.
"Contrary to the figures contained in the Which? report, people are buying more bottled water than last year."
Which? surveyed 3,039 people's water-drinking habits and 48 of its staff to see if they could tell the difference between mineral and tap.
It also says most plastic bottles end up in landfill sites where they take up to 450 years to decompose.