Irvine Welsh needs no introduction. He is a familiar name even to those who have never read any of his half-dozen works of fiction or numerous short stories. The startling success of Trainspotting, the 1996 film adaption of Welsh's novel of the same name, turned what had been an alt-lit classic into a cultural phenomenon. Such is the film's legacy that when I phone Welsh, I half expect Iggy Pop's 'Lust for Life' to kick in when he picks up. Instead I'm greeted by a man a who still speaks with a thick Edinburgh accent, despite not having lived permanently in the city for a number of years.

These days Welsh divides time between Dublin, Miami Beach and Chicago, but still regularly returns to the capital. By his own admission, he just can't seem to keep away. “No matter how long I've been away for, it feels like I've just nipped out for a packet of fags, and I'm waiting to get back. Its weird – when I'm in Edinburgh, I'm thinking I'll be off soon, and when I'm no there, I'm just set on getting back. Its the sort of relationship I have with the place.”

His enduring relationship with Auld Reekie is no surprise. Edinburgh is as central to Welsh as New York was to Fitzgerald; the two are inextricably linked. “Edinburgh's my home town and it's my muse” he admits. “It's the thing that inspires me when I write.”

It was whilst living across the Irish Sea however that Welsh had the idea for his most recent novel, Crime. “Its an existential thriller,” he explains. “It's about a cop who is not so much trying to solve a crime, but trying to solve his own past. The mystery is him rather than what's going on around him.” Set in and around Florida, the cop in question ends up responsible for a young girl who has escaped from a paedophile ring. Why did he choose to write about such a harrowing topic?

“I think a lot of it is to do with living in Ireland. Since the 'Celtic Tiger' phenomenon started, a lot of stuff about paedophilic priests has come to light. Because of the way Ireland is, you know there's no separation of church and state, it's meant traditionally the Roman Catholic church has had a lot of power in things like education, social welfare, etc. It's provided these services direct, so there's always been opportunities for abuse of power. With the increase of affluence with the 'Celtic Tiger', and the secularisation that goes along with affluence, people are coming forward. You can't pick up a newspaper here, or switch on the TV, without someone taking some case against either an individual priest or a diocese. So I think just being saturated in that over here made me very aware of it.”

Crime, despite its subject matter, is not a brutal portrait of social realism in the classic Welsh style. Indeed, the novel marks something of a departure for him. He even describes it as his most uplifting book to date. “The thing about paedophillia, it's just fucking evil. There's no redemption in it. Taking loads of drugs for example, eventually it will fuck people up, but it is good fun as well. People do and say funny things when they are on drugs. With pornography, it's damaging, but it's interesting as well. But there's nothing about paedophilia that's redemptive. You have to be very sober about it. But also with that subject you need to have an upbeat ending I think. Usually I write about people who fuck up, but with this one it couldn't be about that, it had to be about how people heal themselves, how they get through bad times.”

Getting through bad times is something that Welsh has been thinking a lot about recently. Like the rest of the adult populace of the Western world, he has been watching open mouthed at the unfolding global financial meltdown. “Its absolutely fucking obscene. Governments should be regulating these financial markets to make sure abuses can't take place.” Who's to blame, I ask.

“Well it's kind of obvious whose to blame, we've had this kind of society where there is no real politics, there's no alternative to capitalism. It's all about how to make capitalism better. We have to bail out these people who will turn round and continue to exploit us. The great tragedy is that capitalism is a mess, and we just don't have the intellectual resonance to come up with some kind of alternative.”

Welsh could talk about politics all day. He's never short of an opinion on any subject. It was only a matter of time before we touched upon the forthcoming US presidential election. Needless to say, Welsh suspects Obama will take it. “I'm not massively impressed by his politics, but he's got the whole kind of Myspace generation into the political system, which can only be a good thing for democracy. If America slams the door in their face, and elects the usual old, white, country club member type of guy then it will be a terrible disservice to democracy. I think he almost has to win.”

Obama might be the future for America, but what does the future have in store for Welsh? Our old friends Sick Boy and Renton look set to make a reappeareance; Welsh plans to start writing a prequel to Trainspotting at the end of next year. Before that there will be a compilation of various short stories he wrote during the 90s, which will be released next summer under the appropriate title of Re-heated Cabbage. In the mean time, he plans to travel. “I've had a new book out every year for the past four years. I want to kick back and have a bit of fun.” Time then, for Welsh to pop out for fags once more.