She led the pack in a bowler hat, fishnet stockings and towering heels, while the band belted out tracks from new their album Tangled Up.
Back to black: Sarah Harding celebrated her birthday on stage at G-A-Y in London's Soho
The group wowed the crowd at London's G-A-Y night club, and were full of cheers as she blew out candles on a huge chocolate cake.
Fellow band mate Kimberley Walsh also received earliry birthday wishes - she is turning 26 tomorrow.
Hey big suspenders! Party starter Sarah shows off her sexy side
The girls are in the midst of a publicity blitz ahead of the release of their single Call The Shots on November 26, which included an appearance on X Factor earlier that night.
While their career continues to go from strength to strength, the band say they are sympathetic to the current crop of troubled pop stars.
Nadine Coyle has said: "Amy Winehouse is just such a talent, her voice has brought something back that hasn't been around for decades."
Hat trick: the girls are promoting their new album Tangled Up
Dancing queen: Nadine Coyle shows off her moves - and her long pins
Sarah chimed in: "Isn't it weird that the really talented people always seem to crumble under that kind of artistic pressure?"
Cheryl Cole told MTV: "She's absolutely amazing but it's a shame that her personal life overshadows the talent."
Racy: Cheryl Cole and Nicola Roberts vamp it up with the group's back up dancers
Girls wanna have fun: Kimberley Walsh and Nicola Roberts
Nadine added: "Watching Britney has been really hard. There was one picture of her crying on the front of a magazine... I couldn't actually look at the magazine it was disturbing me."
Sarah, who has calmed her partying ways since teaming up with her boyfriend Tom Crane, added: "I just think when it gets a bit much for them then they should be given a bit of space to breathe and get themselves sorted."
Sweet: Sarah Harding was presented with a birthday cake after the performance
