Two supermarkets have denied claims that the economy-price own-brand bottled water they sell is in fact tap water.
The Daily Mail reported that bottles of Tesco Everyday Value Still Water and Asda Smartprice Still Water were sitting on shelves alongside big brands of mineral water such as Evian and Perrier.
But it claimed they were simply a filtered version of what is supplied to almost all domestic homes and that there was no labelling on the bottles saying so.
It was likened to the fictional situation in the sitcom Only Fools And Horses where protagonists Del Boy and Rodney Trotter start selling "Peckham Spring", which is in fact water from the taps of their London council flat.
Both supermarkets denied misleading their customers in any way, saying the bottles gave customers a clear idea of what they were buying.
A spokeswoman for Asda, which gets its bottled water supplied by Yorkshire Water, said it was wrong to call its product tap water.
"Our Smart Price water is treated to remove chlorine, further filtered, then bottled," she said.
"If sparkling, carbon dioxide is added for a bit of fizz. The label on the bottle tells our customers just that.
"Our two-litre bottle is 17p. For comparison - if a customer bought a Brita water filter jug at £16 and used it for the recommended 40 gallons, it would cost 21p to produce two litres of filtered water.
"We're saving our customers time and money - as well as providing a container."
Tesco, whose Everyday Value Still Water also retails for 17p for two litres, painted a similar picture.
"Our Everyday Value Still Water goes through a complex filtration process to improve the taste and remove impurities," a spokeswoman said.
"Tesco sells a wide range of waters to suit all tastes and budgets. All of our products are clearly labelled so customers know what they are buying."
Jeanette Longfield of campaigning ethical food group Sustain told The Daily Mail: "I hope people return to trustworthy tap water - saving money, saving energy and saving waste in the process."