We're close enough to see into his eyes and to watch his chest heave

I Miss You | Beaconsfield, London Oh Lover Boy | Horse Hospital, London

Franko B is the last person you'd expect to see on a fashion catwalk, yet here he is - this compact body, naked beneath a coat of white paint - parading slowly, up and down, up and down, a strip of new canvas. The veins at both arms have been opened and, as he walks, splashes of blood, the colour of crushed crimson, stain the canvas "catwalk". The 200 spectators watch in silence. We're close enough to see the artist's expressive eyes, his heaving chest. There's no music and little sound, except for the whirring of cameras and the distant rumble of overhead trains above Beaconsfield's railway arches, carrying commuters home. That, and the quickening patter of the blood hitting the ground.

Franko B is the last person you'd expect to see on a fashion catwalk, yet here he is - this compact body, naked beneath a coat of white paint - parading slowly, up and down, up and down, a strip of new canvas. The veins at both arms have been opened and, as he walks, splashes of blood, the colour of crushed crimson, stain the canvas "catwalk". The 200 spectators watch in silence. We're close enough to see the artist's expressive eyes, his heaving chest. There's no music and little sound, except for the whirring of cameras and the distant rumble of overhead trains above Beaconsfield's railway arches, carrying commuters home. That, and the quickening patter of the blood hitting the ground.

Of all the visual arts, it is performance art that has perplexed more often than the rest, although there is no reason why this should be so. Good art, whatever its media, frames something and asks questions; the only difference between performance and the plastic arts is the former's essential fragility. It is of the moment, and, as such, is unrepeatable: if this imputes an idea of death, then it should also invite us to cherish life. And Franko B is clear that, whatever other issues his work raises, it is about vitality.

Certainly, it's a vitality that's infused with hard-edged concerns. An Italian artist based in London since graduating from Chelsea Art School in the Eighties, Franko B's body of work - for once, the phrase is literal, as well as figurative - is consistently about exposure and identity. Pain, in as much as it is a constituent part of much of his work, is present because it offers a way of delineating between shared and individual experience. Across town at the Horse Hospital, in "Oh Lover Boy", his current installation of seven door-sized collages - objects include a red, heart-shaped hot-water bottle, gay porn pictures, S&M and medical paraphernalia, an old ticket to a Joseph Beuys show - one feels the absence of anything extraneous. Like "I Miss You", the show's cumulative effect is startlingly intimate. It feels almost intrusive to confront this ten-year collection of memories without appreciating that each one - right down to a franked postage stamp: who sent it? why has their presence been erased? - is emotionally charged.

Receiving its British premiÿre at Beaconsfield's apposite space - its location, on the edge between Vauxhall's "luxury" developments and an older, more resonant London acts as a metaphor for Franko B's liminality - "I Miss You" is Franko B's first "blood performance" since "I'm Not Your Babe" five years ago at the ICA. It's always an uneasy prospect watching his performance work: to see real suffering is hard to endure, but so too is the idea that the spectator is complicit in it. Whereas Franko B's earlier ICA work was "simply" a bleeding piece - viewers encircled him as he stood, then lay, bleeding - "I Miss You" focuses on this complicity with a brutal honesty. In a separate piece called Aktion B, spectators each had a one-to-one encounter with the artist: some cried, others touched his wound. At Beaconsfield, they were encouraged to bring their own cameras to record the 15-minute event and thereby accentuate their active participation.

While Franko B's work has clear antecedents - one thinks not only of Stellarc or Orlan's elaborate performances, but also Chris Burden and the Vienna Actionists, all of whom perpetrated extreme acts on their bodies - it refuses to allow the spectator the prerogative of passivity. Staged a week before Good Friday, one couldn't help thinking of this as a secular passion play, enacted for those whose marginality means that their existence, let alone their suffering, is barely recognised. Detractors might say that this is monstrous work, and in a way it is: the Latin root, monstrare, means to show. If a monster is therefore someone who shows himself as much as he is seen by us, then there is a dignified necessity about Franko B's work. As for the canvas, it's due to be turned into a suit.