British consumers may have been victims of a huge wine swindle, according to fraud investigators who believe some 10 million bottles of cheap Spanish rosé have been illegally sold as more expensive French wine.

The rosé, falsely labelled as ‘vin de France’ (French table wine) or more expensive IGP (protected geographical indication) wine, was sold by four “very large” French distributors, according to Alexandre Chevallier of the French consumer fraud office.

“These cases of Spanish wine fraudulently passed off as French concern more than seven million litres of wine [equivalent to 10 million bottles],” he said.

The results of an investigation carried out in 2016 and 2018 and revealed by Le Parisien newspaper on Monday have shocked France. For many French wine drinkers, rosé is the summer tipple of choice. Consumption has risen sharply during the current heatwave in much of the country.

Britain is one of the largest export markets for French rosés and investigators believe some bottles may have ended up in the UK.

Criminal proceedings are about to be launched, officials said, but they have not named the vineyards or merchants accused, or revealed whether arrests have been made. If convicted of fraud, vendors risk lengthy prison terms and hefty fines.