Vodka brands, including Smirnoff, Absolut and Polish brand Wyborowa, are now outselling traditional blended whiskies such as Bell's, Teacher's and Famous Grouse, according to figures published in Off Licence News.
The figures reveal that £747m was spent on vodka in shops, supermarkets and off-licences in the 12 months to April, a rise of 11% in one year, whereas sales of blended Scotch have only increased by 1% to £742m.
Total whisky sales, including expensive single malts, still outperform vodka with £872m spent last year but experts predict that vodka will take the top spot by the end of the year.
Vodka has been the best-selling spirit in pubs and bars for a long time, but this is the first time it has become more popular in the off-licence trade, where tastes are more traditional.
Some analysts believe that vodka is benefiting from its cool image, while whisky is seen as more of an "old man's" drink.
Rosie Davenport, news editor of Off Licence News, said: "This is a landmark moment for one of our most treasured drinks. While Scotch has lots of heritage, which has propelled sales overseas, at home it's had a tough time appealing to a younger audience."
At the end of last year, Pernod Ricard focused on the traditional Polish origins of its Wyborowa vodka brand in a humorous campaign, created by Wieden & Kennedy Amsterdam, which argued that the spirit should be called "wodka", as in the original Polish spelling.