The figure more than doubles the existing record of 9.5 million set the previous week, and is three times the figure for the same period a year ago.
It is thought that sales were boosted by the number of people who received MP3 players and download gift vouchers for Christmas.
Despite the rise, illegal downloads still far outstrip the legal counterparts. Peer-to-peer monitoring service Big Champagne estimates that at least 250 million tracks are downloaded worldwide every week from file-swapping services.
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