'That's the worst shirt I've ever seen," says Bob Geldof by way of introduction. The formalities out of the way, he leans back on the couch of a club in Soho, swirls some black coffee around his mouth, tries in vain to light the stub end of a cigar and declares:

"The last five years of my life have been a Shakespearean tragedy. The grief, loss, pain, bewilderment, anger" - his head nods forwards to punctuate each word. "You know, what the f**k is going on? Is someone taking the piss? This . . . spectator sport, this . . . soap opera."

He peers over his sunglasses, leans forwards and says ominously: "I'm afraid now of the next episode. The problem is, I will step into the scene, whoever is writing it, and I know it's going to be just too much. And I just wish it wasn't. I really wish it wasn't."

There's desperation in his voice. "How far down does this thing go? How do I get out of this? I'm angry that any of this should have happened at all. The level of tragedy. The bewilderment. The piteous cruelty of it all. The sitting there dumbstruck by events.

"I didn't talk about it at the time. Everybody was going, 'Tell your side of the story', but I couldn't talk about what happened. Some things are unsayable. Everyone knows the characters involved, but I wouldn't go into the pornography of intrusion. I mean, how do you articulate the unspeakable?"

By the articulate speech of the heart, it would seem. Geldof's new album, his first for nine years, is a 10-track cathartic release that should come with an emotional-health warning. Called Sex Age & Death, it's a primal-scream session set to music.

"I know it's a bloody clichΘ, but I was using the higher language of music to articulate my feelings, to describe this 'felt' thing, to encapsulate my experiences."

Those experiences are well known, not least because, as Geldof, three months away from his 50th birthday, points out, "they were made for the tabloids".

The Boomtown Rats singer and instigator of Band Aid and Live Aid, who is perhaps now best described as a businessman and lobbyist, was divorced from Paula Yates in 1996, after a 19-year relationship.

After a bitter court battle, he won custody of their three daughters. Yates and her new boyfriend, the rock star Michael Hutchence, had a baby daughter in August, 1996. A year later, Hutchence was found hanged in his Sydney hotel room. Geldof was the last person he had talked to, in a vicious telephone row over Yates's rights to see her children. In September of last year, she was found dead in her bed, after overdosing on heroin.

This tragic series of events lingers around Sex Age & Death. On My Birthday Suit, a heart-breaking ode to Yates, he sings: "And everything we've been has been undone / And everything we did is been and gone and left unsung / I meant to say I thought you knew / I always prayed for me and you / But never mind, it doesn't matter now."

The lyrics are all the more significant when he explains that he wrote the album after his divorce but before Yates died. He wrote one of them, Scream In Vain, after the death of Hutchence.

"You got a life and left me for dead / What the f**k is going on inside your head? / So why put a noose around your neck? / What the f**k is going on inside your head?"

"Scream In Vain is pointed, focused and direct, and it was written about my whole bewilderment with the situation," he says. "Yes, there is a line in there about an individual, but it is more about the tragedy of it all. Everyone knows who is involved."

However terse he is about the "individual", he's lovingly loquacious about Yates. When reminded that she used to complain that he never wrote her a love song when they were together, he gets animated. "She was wrong. There was a song on Mondo Bongo [The Boomtown Rats' fourth album] called Fall Down, which was for her".

He sits up straight and recites the lyrics: "Put your head between your knees and breathe real deep, let it in, let it out until it's over. I might scribble, I might scrawl, I might storm and rage and thunder. Oh Christ, but then later in the incinerator, something inside seems to fall asunder. I need to scream every now and again. Try to understand it's only me. Not only cripples have a need for crutches. And if they ever take you away from me, I'd fall down."

His eyes well up.

"And I did. That was for her. When I wrote it, I didn't want to sing it. Simon Crowe, the Rats' drummer had a beautiful voice, really pure; he sounded like a choirboy. So I wanted him to sing it. But I did it in the end. I'm sad Paula isn't around to hear the songs . . . I'm sad she's not around. I cried for years when she left me. I cried until there were no tears left."

He fell a great distance when Yates left him. "I just couldn't function," he says. "The only words to describe it are biological: I was barren and sterile. I was eviscerated and emasculated. There was a physical impact to what happened to me.

"You know, the heart is the locus of all pain, and I felt it there, and I felt it in my ribcage. I really thought I was going to die of a heart attack. I went to the doctor and he put me on beta blockers, but I didn't like them, so I stopped taking them.

"The pain was situated in my gut, and I would take out this ball of pain from my gut, look at it and say, 'So that's what you look like,' and then put it back again. I couldn't feel anything from my waist down . . . I couldn't get a hard-on."

All of this happened in the two years after Yates left him. His friends took action. "They just moved in with me, all my male friends. I didn't notice them moving in, but they did. I'm very up on men at the moment: men are cool. It wasn't a male gestalt group thing or anything; they were just around.

"Pete Briquette the bass player from the Boomtown Rats, who I've known for 26 years, moved in and started setting up this recording equipment in the basement. I went down there once and picked up this bass guitar and just hit this string over and over, and he was like: 'Hello?'.

"I've no recollection at all of beginning this record. Although I do remember finishing it. And then some girlfriends would call around, and they were so kind and intuitive. I really needed to feel like a man again, because I was, as I said, emasculated by what happened to me.

"They would be picking out clothes from my wardrobe for me to wear and telling me what I looked good in. They made me feel desirable again. They'd say, 'Come on, we're going out,' and I'd be, 'No way,' but they'd force me. And they'd hire a limo, which I hate, and I'd be arriving somewhere with these two beautiful women on my arm and the cameras would be going f**king mad.

"I know what happened to me has also happened to a huge number of people, but it just seemed, in my case, to be so extreme," he says.

"But then my whole life has been extreme and so episodic. I've literally lived it in episodes: there's Boomtown Bob, Band Aid Bob, Businessman Bob, Paula's Bob, Sir Bob, Saint Bob . . . you can see which one is in people's eyes when they approach you. I really didn't set out to live my life this way, and that's why I'm afraid of the next scene.

"The problem, I think, is that you could put an idea or proposition to me now and I'd go, 'That's f**king interesting,' and off I'd go on this tangent. It's because it excites me, it excites me intellectually. It's the road less travelled, and sometimes, in my case, the consequences are bizarre.

"Like Band Aid and Live Aid. When we decided to do the Band Aid single, someone turned around to me and said, 'You're writing the song,' and at the time, the Boomtown Rats were has-beens, our time had been and gone. I was f**king mortified: we were stiffs, and I was supposed to write this song for all these stellar people to sing.

"I had this old song that the band had rejected years previously, and the opening lines were, 'It's my world, and there's no need to be afraid,' and I used that as a jump-off point; the chords were the same. Then all of that lead inevitably to Live Aid. That's how things work for me: I get bored and start on something."

After Live Aid and the withering away of the Boomtown Rats, he got involved in television and radio, setting up the Planet 24 production company, which gave us The Big Breakfast. More recently, he's been involved in a rash of dotcoms.

He's also a belligerent and effective lobbyist for the cancellation of Third World debt, but he still stubbornly refers to himself as a musician - "well, OK, I'm a musician who does other things as well. I do this other stuff because I can. I don't call myself a musician because I make records. I'm a musician because it's my essence.

"To be honest, the business end of what I do doesn't occupy that much head space: you're involved in empirical events like a deal or something. But I'm not that moved or involved in it beyond that moment. There isn't that complete sensation of involvement that I get from music - that satisfaction of a great gig or writing a great song - well, a gig or a song that I think is great but other people might think is shit."

What you hear is what you get with Geldof. The only way to hold a conversation with him, such is the passion and intensity of his beliefs, is to talk louder and longer than him to get a question through. He has a remarkable grasp of geopolitical issues and a treasure trove of anecdotes about world leaders and rock stars that he insists, sadly, remains off the record.

Such is his persuasive eloquence that after a 20-minute lecture on why Margaret Thatcher was the first punk rocker, you almost find yourself agreeing with him. And he doesn't mind if you tell him he's talking rubbish.

Though now more than 20 years living outside the Republic, he is still moved by it to paroxysms of righteous anger. "What I think is fantastic now is the meltdown of the political consensus that pertained, as evidenced through the tribunals.

"Yes, I know the Boomtown Rats were of minor importance, but we were the first to post these Lutherian ideas on the church door, and we spoke up against that de Valera cosy consensus of church state when we started out, in 1975. We were saying back then that this was no longer where it was going to be at. And remember, in 1975 in Ireland, for the first time, 50 per cent of the population were under 25.

"Somebody pulled out my first interview for me recently, and in it I was gabbing on about how I was going to 'change this place', and maybe we were the first knock on the door. Certainly, our songs grasped at an understanding of that. I hope the tribunals are the end process of what we helped to begin. That could be our legacy.

". . . So when I read what's happening now at the tribunals I just go: 'Yes! Yes!' I'm back a lot, and the changes are everywhere.

"There's bad stuff too, though. The intolerance towards asylum-seekers - that coming from us, who asked the world to take us in for so long. And this dreadful nonsense of the Celtic Tiger - such a hubristic expression.

"I'll tell you who the real tigers are, and it's the men and women who came to Britain in the 1950s, who we've forgotten about. You see them now and it's awful, these helpless, homeless and deracinated people. We've abandoned them.

"It's wrong. We owe these people such a debt. They kept us going. They sent back their wages to us. We have to take them back. We have to reclaim them and honour them. Really, we do."

He pauses to ensure that you have taken in his message, then relaunches. "And these people who come to us, looking for asylum. We must absorb them and take them in. They've so much to give us. Not just economically, but spiritually and culturally.

"Look what the Irish gave the Yanks: let them give that to us. Look at what we gave Britain: Johnny Rotten, Morrissey, Oasis, Boy George. I always know a Paddy over here - they're the ones that are always going "No" or "Why?" when it comes to authority.

"We see authority as something to be tolerated, not respected. We have to stay open to ideas and other people, not close down. Otherwise it will just be a country of people complaining about house prices."

Some of the papers say he is going to be our next president. What's the story there?

"I wouldn't be able to make albums or go on tour if I did that. I don't know, I think people are sick of me twatting on and on about things. What's the money like?"

Sex Age & Death is released on Monday by Eagle Records