The room is packed with teen girls and young women, all squealing and seething with sexual desire. The object of their giddy affections isn't a ditzy male heart-throb such as Craig David or Robbie Williams, however, but a sharp, opinionated, fervent punk activist called Kathleen Hanna. In the early 1990s, long before the Spice Girls figured out that the words "girl power" could be an effective marketing tool, Hanna was a key player in the empowering riot grrrl movement. Fronting the band Bikini Kill, she scrawled "slut" across her belly and raged against the inequalities behind such a word. If she is calmer these days, it's only in appearance: the anger and conviction that fire her performance with her new band Le Tigre are as fierce and exhilarating as ever.
Joined by guitarist Johanna Fateman (ragged peroxide hair and thrift-store chic) and keyboardist Sadie Benning (absent tonight, and replaced by an androgynous-looking person called JD), Hanna aims to merge politics with pop in a manner that has been scoffed at for decades. Le Tigre's manifesto is encapsulated in Slideshow at Free University: it didn't sound like much on last year's debut album, but live, accompanied by images of protest marches, it's a stimulating piece of work. Over a hypnotic, gloopy groove, a man's voice intones: "We favour the simple expression of the complex thought."
The trio's music is correspondingly basic: a gritty garage-pop assault of scrawling guitar and pogo rhythms, against which gender, race and sexual politics are distilled into shout-along anthems, incomprehensibly but coruscatingly yelped by Hanna, attacking New York mayor Rudy Giuliani in My My Metrocard, the misogyny of film-maker John Cassavetes in What's Yr Take on Cassavetes, and the artists who contribute nothing to social change in The Empty. The results could be glib, but Le Tigre are too passionate, too committed for that to be the case. A new song about racism ends with the trio chanting the numbers from one to 41, the number of times the west African immigrant Amadou Diallo was shot by New York police. It's simple but brutally effective.
"The artists," continues the voice on Slideshow, "wanted [their art] to be something to be involved in." And so Hanna and Fateman introduce each song with spirited rallying cries inspiring their audience to engage in politics, to fight against discrimination, be it on the internet, on the streets, in a joke or in a pop song. In return, the panting young ladies in the front rows take up an incessant chant: "Kathleen, you rock." There's something disappointingly inane about their reaction - they almost deserve the Spice Girls instead. Then again, that might be the most brilliant thing about Le Tigre: they can be political without being po-faced; they can discuss weighty issues and be go-go dancing at the same time. They are serious and playful and the kind of role models every teenage girl needs.
• Le Tigre play the 13th Note, Glasgow (0141-243 2177), tomorrow.
