After an intense conversation with Annie Lennox, I am convinced I know why she does the things she does. If that sounds presumptuous, I can only say that rock music has always provoked bold, bald statements. First, she has suffered from bouts of depression since she was 14 in her home town of Aberdeen; secondly, her father and grandfather were trade unionists of the old school, committed to improving the lot of the underdog.

“Many people,” she says, “have a fairly s****y life.” She is not trying to include herself in the category, although she has had her moments. “I love people who have principles and stick by them.” Again, she doesn’t claim to be of their number, only to want to “put the ideals that I have into some kind of symmetry with what I do for a living”.

Now 52, she says these things with the same fervour she has brought to her singing these past 30 years with the Eurythmics and as a soloist. Regularly called the greatest white soul singer alive, she is a musical counterpart to the conviction politician. As a result of this, not to mention her feminism and her striking androgyny, some regard her as scary, whereas the truth is surely that she is passionate.

“If I were just promoting my records,” she goes on, “I would be disgusted with myself.” As with the delivery of the songs – Would I Lie to You? springs to mind – she dares you to doubt her. Still, there is no getting around the fact that she is releasing a new album called Songs of Mass Destruction. It contains several moving compositions that come from this rueful vision of hers. Last month she headlined an Albert Hall concert for Peace One Day, the organisation behind the UN’s adoption of September 21 as a fixed date in the calendar for conflicts to be suspended. Her half-hour set, which included the new single, Dark Road, had a blistering honesty about it, and an absence of ego that seemed appropriate to the occasion. On that showing, it would be hard to argue with her own assessment that her voice is in its prime and that she is “closer to my cutting edge than ever before”.

Lennox’s involvement with this organisation started several years ago when she attended an event it had put on at Brixton Academy and was asked to read out a speech written by the Dalai Lama. When she talks about this and her other great involvement, with the South African Aids activists’ group TAC (Treatment Action Campaign), she does so with an energy that leaves you in no doubt that these callings are as urgent to her as was her teenage music vocation. She recalls her sense of awe at seeing Nelson Mandela standing outside his old cell on Robben Island rejoicing in the defeat of apartheid but warning of the greater struggle against the “genocide” of Aids.

Aids has now become for her not only a cause to be helped financially, but a theme of her songwriting. On Songs of Mass Destruction there is one called Sing, which incorporates a track by the TAC members group called the Generics. As message songs go, it carries a highly specific one, calling for the national implementation of a programme to prevent HIV transmission from mothers to babies. Lennox contacted 23 female singers of global renown, asking them to join her on the recording; hence the presence of Madonna, Céline Dion, kd lang, Beverley Knight, Sarah McLachlan, Shakira, KT Tunstall, Martha Wainwright, Bonnie Raitt, Joss Stone, Gladys Knight and others.

The idea is to put the track on the internet, with the profits from downloads sent to support TAC initiatives. You could see this as a practical enactment of the Eurythmics’ 1985 hit with Aretha Franklin, Sisters are Doin’ it for Themselves; whatever else it is, or does, it is a huge feminist anthem, with the endorsement of the ultimate girls’ superchoir.

“I can’t understand why it [feminism] has become such a scurvy word,” says Lennox. “I find that odd. I think people are a little scared to use it. I’m not. I’m saying it loud and strong. When I go to poor countries and see women labouring in the fields, carrying loads on their back as well as children, I think that what they need is empowerment. You can be a man and a feminist, too. It’s just about social and political rights. Until women finally get a better deal, we need feminism.

“Something happened, around the 1980s, when women started to become ashamed. Maybe there were a few too many brazen hussies, and maybe that was a bit of a turn-off, I don’t know. But you have to remember that women died for the vote and we still don’t have equal rights. Many men are quite threatened, I know, by the new phenomenon of women. I understand that; the male ego can be a frail thing – so too can the female, actually – and here are women getting top jobs. On a personal level it must be threatening.”

She has a top job. Is she threatening to men?

“Yes, I think so. Although never at all intentionally.”

But she is ballsy, as a performer. That is generally meant, as here, as a compliment.

“I take it as one . . . I really do have this intensity and energy, I know. I can’t help it, it’s just who I am. Seriously, I often have the sense that I should dampen it down to accommodate certain men.”

Not that there is a particular one in her life at present. She has been married twice, the first time very briefly to Radha Raman, a Hare Krishna monk, in the mid1980s; the second time, between 1988 and 2000, to the film producer Uri Fruchtmann, the father of her two teenage daughters, Lola and Tali. Her present singleness appears to suit her.

“It is probably better for me,” she agrees. “To be honest, I think relationships can be too difficult, very complicated. There is a part of me that thinks I could fare better in a close relationship with a man, but then, as I say, it all gets too complicated. It hasn’t panned out. It never did.”

But she gets on with her exes? “I have to sidestep that one because it’s too tricky. I’m sorry.”

She must be doing something right; she looks terrific, less gaunt than a few years ago, with a voice that sounds more flexible, broader and more relaxed than in her early years after she had left the Royal Academy of Music in London (where she studied the flute.)

She says her life has all been “a bit of a rollercoaster”, and that she is trying to smooth it out. It “feels big and extraordinary” when she is away singing, but she gets “heartsick” for her daughters and longs to be back in the smallness and sanity of Crouch End in North London.

And the depression? “Here’s the deal. It’s insidious. You can’t put your finger on it. You feel dreadful and you think there should be a reason. Stephen Fry [in his recent TV programme on the subject] described it very well when he got out of the car, in Aberdeen actually, saying: ‘I just feel dreadful.’ He described it and I knew exactly how he felt.” And it wasn’t because of Aberdeen? “On that I shall remain schtum.”

But not on Amy Winehouse, the troubled young singer who has some claim to being the next rock diva. “Oh, I think Amy has been given an incredible voice and writing skills. I saw her at the Cobden Club (in north Kensington) when she was 18, and I was completely blown away. She was like a woman in her thirties, with a whole, seasoned delivery, not fazed by anything at all. I was in awe of her. I thought, wow, you have a special talent. God, you are 18, where did that come from? I am very concerned for her. She could just destruct. There is some issue that desperately needs to be handled. When I talk about Amy, I think, there but for the grace of God. Not with drugs or drink. I think I have other issues.”

The depression? “Yes.” But then she also has a range of strategies, which includes her friends, her family, the music and the purposes she puts it to. She also has that not too common British attribute of pure, ardent exuberance at the heart of her. This may sound like a contradiction of the depression but it is in fact a travelling companion, the sort which reminds her that, having come so far, there’s no backing down now. The stakes have become too high.

Annie Lennox’s new CD, Songs of Mass Destruction, is out on Sony

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