Digital sales now make up 98 percent of the singles market.
The New York singer, 23, known for her outlandish dress sense, topped the all-time chart, with US band Kings of Leon also among the most downloaded artists.
“Poker Face” notched up 779,000 sales on downloads, while “Just Dance”, her first single release in Britain, came third in the chart with 700,000 sales.
“Sex on Fire” by Kings of Leon came second, while the Tennessee family were also fourth with “Use Somebody”. British electropop duo La Roux’s “In For The Kill” — the most recent release in the top 10 — was at number five.
The top five were all released within the past 12 months, indicating the importance of download sales to the music industry.
The Official Download Chart was launched in September 2004 to reflect the most popular tracks within the new legitimate download business.
“This is a fabulous achievement from Lady Gaga, to come from nowhere in January to dominating the all-time downloads list with two in the top three,” said charts company managing director Martin Talbot.
“Her success — and that of Kings Of Leon and Leona Lewis, too — reflect the resurgent success of the singles market in the era of the download and highlights that mass appeal pop music is alive and well in 2009.”
Lady Gaga said: “I am honoured to be the songwriter and performer behind the number one and number three all-time most downloaded songs in history in the UK.”
All-time British official downloads top 10:
1 “Poker Face” — Lady Gaga
2 “Sex On Fire” — Kings Of Leon
3 “Just Dance” — Lady Gaga
4 “Use Somebody” — Kings Of Leon
5 “In For The Kill” — La Roux
6 “Run” — Leona Lewis
7 “Hallelujah” — Alexandra Burke
8 “Bleeding Love” — Leona Lewis
9 “Chasing Cars” — Snow Patrol
10 “Rockstar” — Nickelback
Most downloaded song – comments and views