Ke$ha's debut release Tik Tok was the biggest-selling digital single in the world last year.
It sold 12.8 million copies - three million more than Lady Gaga's Poker Face, which topped the chart in 2009.
The track, which originally got to number four in the UK singles chart, was ahead of Lady Gaga's Bad Romance and Eminem's Love The Way You Lie in the 2010 chart.
The sales figures were released in the annual digital musical report published by the International Federation of the Phonographic Industry (IFPI).
The industry body, which represents 1,400 record companies in 66 countries, said worldwide digital revenues had gone up by 6% to 4.6 billion US dollars (£2.8 billion) but piracy was still costing jobs.
IFPI chief executive Frances Moore said: "As we enter 2011, digital piracy, and the lack of adequate legal tools to fight it, remains the biggest threat to the future of creative industries.
"Great new legitimate music offerings exist all over the world, offering consumers a wide range of ways to access music.
"Yet they operate in a market that is rigged by piracy, and they will not survive if action is not taken to address this fundamental problem. This is the challenge and the opportunity for governments to seize in 2011."
The report revealed sales of digital albums rose 29% in the UK, but stated digital piracy is "growing rapidly" and illegal file-sharing remains "rife" with 76% of music obtained online in the UK unlicensed.