"Most people", says Robert Del Naja, "choose to ignore things on a daily basis. Whatever paper you choose to pick up in the newsagents in the morning, or whatever sites you go to to get your information define you. Are you going to read trivia and watch the movie channels or talent shows on TV, or are you going to go to the news and history channels and find out shit?"  Not one to follow anyone's diktats, Del Naja has refused to be boxed in. Although most people will know him through Massive Attack, which he helped found in 1988, Del Naja was a graffiti artist long before he was a vocalist. He began painting in the early 80s, at a time when graffiti was mainly a way of venting anger against a Thatcher government. When Banksy was barely out of nappies, Del Naja was venturing out onto the streets of Bristol. "I went out on my own one fabled night in 1983 and just took a bag of paint out and a pretty crappy drawing and started," he says.  With no formal training (apart from an ungraded A-level), his art education was not conventional. "The graffiti thing got me out of the classroom into doing something I was actually inspired to do," he says. "I was looking at the work of the New York street artists and then discovering Basquiat and Haring after that and seeing how the contemporary art scene was, and then going back into Warhol and all that was happening in the 60s. So I learned backwards, in a sense, from the street into the gallery. And now I'm re-educating myself again with all the great new street artists. It keeps going round."  Banksy's name inevitably pops up, but Del Naja is unimpressed by the recent hoo-hah surrounding his work. "I think the problem with the art market and the art scene is that it is its own beast," he says. "It thrives and breathes and defecates independently of the artist."  Even so, Del Naja clearly has a lot of time for the younger artist. "When you look at Banksy's work as a catalogue of ideas, it's undeniably brilliant. Going back to my days doing stencil work back in the 80s I knew that it wasn't exactly the most demanding work: it's like printing, but then Warhol was a printer. It's the image, it's the phrasing, it's the timing of it, it's the placing of it. It's when and where you do it. And [Banksy] is unsurpassed in that kind of work."  Earlier this year Del Naja's own return to the art world materialised with a major exhibition of new paintings, War Paint. It took place at Lazarides Gallery, whose owner, Steve Lazarides, also has Banksy and cult comic artist Jamie Hewlett on his books. Part of the Banksy posse and old pals from the early Bristol days, Lazarides was instrumental in Del Naja's return to the scene.  War Paint (the title is Del Naja's own) included 12 of his paintings, which were inspired by the artwork he did for James Lavelle's album, War Stories, released in 2007. Painted in iridescent reds and dark shadows, the ghostly, skeletal figures in the paintings recall martyrs or saints. One of his more recent works, Peace at Last, which was developed from the album cover image, he sees "almost like a Mexican Day of the Dead festival."  "It felt like a mural you'd find on a wall somewhere, in a place where tumbleweed might be blowing around because something had happened there and everyone had since departed."  An unlikely source of inspiration, given his uncompromising views on religion ("it always causes damage"), are Del Naja's Catholic roots. "I've always been interested in Catholic iconography. My dad's from Naples and I was brought up in a Roman Catholic school. I could try and be romantic and say it had a profound effect on my life, but I don't remember much about it. I do remember hating it and being scared of it, though. In terms of the imagery I find it amazing."  The image of Christ infiltrates his War paintings. The figure in Unbelievable, like many of his others, is haloed and has a stigmatic stain in the shape of a cross, soaked onto his solar plexus. "A lot of the imagery was very obvious", he says, "and I was slightly concerned because James had called the album War Stories and that with my paintings and his title, the whole thing might suddenly be too direct and not intriguing enough." He needn't have worried; the exhibition enticed a stellar crowd to the gallery on its opening night.  Lavelle, who founded music outfit UNKLE in 1994, like Lazarides, has always been a big supporter of Del Naja's artwork. "When I was still very disinclined to get my ass into the studio, he was always the person who tried to get me back into my painting. James's input always kept me buzzing underneath." It was Lavelle too who advised Del Naja to go back to painting in red and black, the colours that have come to define his bloody, dark artwork.  "The red and black thing for me has been a thing from back in the day. My favourite album sleeve of all time is Inflammable Material by Stiff Little Fingers, which is the black sleeve with acid red text on it and the grey flammable logo, which I wanted to use for the first Massive Attack album, to add this complete connection to me because that's what I grew up with."  Just as it was back in the Wild Bunch days, it's also been Del Naja's job to sort out the posters and backdrops for the Southbank's Meltdown festival (he and bandmate Grant Marshall are this year's artistic directors). He considers this visual process "more exciting than the music, ironically". He's currently finishing a series of national flags painted in red and black, which are due to hang inside the Royal Festival Hall.  The countries represented are those on which Britain has had a negative effect on over the past century or so. A blacked-up Union Jack and a bloodied Stars and Stripes will hang alongside the other flags - just as well, he says: "I've got the chance to fuck off the British establishment and all of the extreme countries that we've completely fucked over in the last hundred years all at the same time."  Despite the anti-establishment talk and his scepticism about the market, Del Naja admits he's actually rather smitten with the whole art thing. "I'm a consumer of it all and now I've fucking started collecting shit, whether it's comics, toys, books, now it's fucking art. My collection is modest, but I do love it. I've got this terrible magpie-like nature when I go to a gallery; I just want things. "I fucking want it on my wall, I want to own it. I don't know where it comes from. I need to get a grip."  Meltdown runs at the Southbank Centre, London, from June 24 2008, tickets 0871 663 2500
Anny Shaw speaks to graffiti artist, Massive Attack founder and Meltdown festival curator Robert Del Naja about street art