Gaga, dressed in a ghostly carnival headdress and skimpy lace outfit, picked up awards for International Female Solo Artist, International Breakthrough Act and Best International Album for "The Fame,” winning every category in which she was nominated.
The singer, on top of the British music charts for most of the last 12 months, dedicated an eerie live performance to fashion designer Alexander McQueen, who died last week.
"Thank you so much for believing in me," she told her fans.
British boy band JLS, who finished second in TV talent show "The X Factor" in 2008, polished off a year of number one singles and a top-selling album with two awards - best British group and best British single for "Beat Again.”
Lily Allen was crowned best British female artist and Dizzee Rascal was named best British male, capping his successful transition from rapper to bona fide pop star.
Rascal's latest album "Tongue N' Cheek" has yielded three number one singles - "Dance Wiv Me,” "Holiday" and "Bonkers" - which have had as much to do with house music as rap.
It was a big night for hip hop. US rapper Jay-Z won the International Male Solo Artist award and delivered a powerful rendition of his hit "Empire State of Mind" with Alicia Keys.
Jay-Z's star has been on the rise in Britain since he won over thousands of new fans as the first hip hop act to headline the Glastonbury festival in 2008, traditionally a rock event.
"We proved that hip hop could play anywhere in the world," Jay-Z said.
Pomp and ceremony
The event, which has been criticized for failing to recognise artists beyond the major labels, brings together hordes of record company executives, artists and hangers-on to celebrate the previous year's successes at London's Earls Court.
"Twenty minutes of entertainment dragged over a two-hour show," cracked presenter comedian Peter Kay.
Undeterred by a wet winter's night, hundreds of star-struck fans toughed it out outside the west London venue hoping to catch a glimpse of their idols.
The event has become known for overblown performances by the winning artists and Tuesday ran true to form.
Allen opened the night with a rendition of "The Fear,” backed by male dancers who dropped to the stage dressed in pink camouflage, brandishing machine guns and Union Jack umbrellas.
Indie rockers Kasabian, winners of best British group, played their song "Fire" behind a wall of flames and the four members of JLS began "Beat Again" as four crucifixes hung high above the stage.
Oasis singer Liam Gallagher produced the night's only moment of mischief, tossing his microphone and award into the crowd after accepting the BRITs Album of 30 Years for their 1995 album "(What's the Story) Morning Glory?.”
Florence and the Machine grabbed the best album award for "Lungs" and former Take That member Robbie Williams, who went on to success as a solo artist, received an Outstanding Contribution to Music award.
"Yeah, I've chipped in," said Williams, who delivered a medley of hits such as "Angels.” "Odds and sods over the years."
