Sainsbury’s Blanc de Blancs Brut Champagne came joint top with a score of 80 out of 100, sharing the accolade with Piper- Heidsieck Brut Champagne. Tesco came third with its Finest Premier Cru Champagne.
The consumer affairs organisation said the results showed that “price doesn’t necessarily guarantee quality”.
The top-scoring non- Champagne sparkler was the Co-operative Group’s Prosecco, followed by a tie between Tesco Finest Blanquette de Limoux and Waitrose Valdo Oro Puro Prosecco Superiore Valdobbiadene.
Supermarkets were asked to nominate one own or exclusive- label NV Brut Champagne and one sparkling wine for the test.
These were tasted against leading branded Champagnes and sparkling wines by Tim Atkin MW, Peter McCombie MW, Kathryn McWhirter, Charles Metcalfe and Derek Smedley MW.
Which? also tracked Champagne prices for more than a year and found the Piper-Heidsieck that came joint top in the taste test was on sale in Asda for 62 days of the year at £18, a £15 reduction on its rrp.
Which? editor Richard Headland said: “Christmas can be expensive so it’s satisfying to see our festive taste tests revealed some of the cheapest were also some of the best. Time and again, we find supermarket own-labels giving the big brands and high-end retailers a real run for their money.”