LORRAINE McIntosh could give me details of the character she plays in the new Still Game stage show, but she’d have to kill me. That’s how much of a closely guarded secret the plot of the forthcoming Hydro extravaganza is. Being a journalist, however, means I can’t stop myself from trying to pump more information out of her and following an early admission that McIntosh finds it hard to keep secrets, I try various strategies to make her spill the beans. To her credit the actor and Deacon Blue singer remains tight-lipped.

“I want to tell you,” McIntosh giggles. “But I really, really can’t. Greg and Ford [Still Game stars and writers Hemphill and Kiernan] would kill me. And probably you as well.”

After spending an afternoon in her company I can see why McIntosh might find it hard to keep secrets: it’s the openness and enthusiasm of her conversation, the wish to empathise with what you’re saying, to find out about you and your life, your story. When you’re that sort of person you can’t help but divulge things. And McIntosh is that sort of person.

It is these attributes that make the 52-year-old mother-of-three such enjoyable company, of course, whether the topic involves the politicisation of young people in the lead-up to the 2014 independence referendum, high street shopping or Bruce Springsteen’s recent autobiography, and we cover all these things before I even switch on my recording device.

Now, though, we’re talking about being in a successful pop group for 30-odd years. Just about everybody in Scotland has a favourite Deacon Blue song. For many it is Dignity, the best-known track from 1987 album Raintown (written, like the majority of band’s music, by McIntosh’s husband of 26 years, Ricky Ross), which tells of a council worker saving his money to buy a wee sailing boat, famously called Dignity. What it is really about, of course, is decent working-class people living quiet, dignified lives and in that way it’s classic Deacon Blue: packing an emotional punch, wrapped up in a catchy pop tune. And, in common with much of the group’s output, it is steeped in Glasgow.

What’s it like, I wonder, to live in the city where your music has become part of the narrative of its people? McIntosh is well aware of the special place the songs have in people’s lives.

“It’s amazing and really lovely, especially for Ricky,” she says. “You go through a stage when you’re younger and a bit more arrogant when you say, ‘I wish they’d talk about another song [than Dignity]’. Then you grow up a bit and realise how lucky we are that so many people feel the need to tell you how important a song has been in their lives. And it’s not just Dignity – songs like Loaded, Chocolate Girl and Wages Day also mean a lot to people.

“A few years ago we were playing Hogmanay in George Square in Glasgow. It was freezing when we were sound-checking in the afternoon and the only people around were the council workers putting out the grit. We would never normally do Dignity at a soundcheck, but one of the council guys shouted out, ‘Come on Ricky, do Dignity for us.” And we looked at each other and said – why not, let’s do it. And we did. It was absolutely brilliant – the song was about them and they knew it. It was such a lovely moment.”

There have been many great moments over the last 30 years with Deacon Blue, says McIntosh, who was just 22 when she started touring with the band, and there are many more to come, including a gig at Edinburgh Castle in July. Since the release of Raintown the band has racked up 12 top-20 singles and two number one albums, touring the world in the process and becoming one of Scotland’s most successful ever groups. Recent album Believers was critically acclaimed and made the UK top 20.

For a music-mad young working-class girl from Cumnock, Ayrshire, it’s been an extraordinary journey. But she admits the early days were difficult, especially as there were few female friends around to share the experience with.

“It was tough hanging out with men all the time,” McIntosh says. “I was so young and I used to get so homesick. We’d be on a tour bus driving down the M6 and I’d be in tears wanting to go home.

“For all it was exciting, I used to find it really lonely and I missed my friends. I actually lost quite a lot of friends during that time because for pretty much eight years solid I was away from home. And every record company meeting you went to would be full of men. The music business was very male-dominated then – it still is. We had a female tour manager, Gill, who was brilliant and really looked out for me. If it hadn’t been for her I don’t know what I would have done.”

McIntosh, who lives in the south side of Glasgow with Ross and their 16-year-old son Seamus, says it is heartening to see so many more women writing, making and selling music both as solo performers and in bands. But she is scathing of a music business and media that heaps pressure on female performers – even those at the very top of the business – to be hyper-sexual and promote their bodies alongside the music. She can recall only one occasion when she felt under pressure to look more sexualised, after making the video for the single Loaded in 1987.

“I look back now and smile at how unsophisticated we were,” she says. “I remember shopping in Miss Selfridge for the top for that video and just wearing whatever else I had with me, including a pair of over-the-knee socks. After that a guy from the record company sent a memo saying that I was to wear these socks again. I remember saying there was no way any man was going to tell me what I was to wear. But that was the end of it – they never hassled me again.

“It wasn’t that we didn’t want to look attractive in the 1980s, it was more that we wanted to look cool. Look at Bananarama in their dungarees and T-shirts – they looked very ‘art school’ cool. And the look Annie Lennox created, the men’s suits and shaved head, was absolutely stunning.

“Now I feel so sad when I see how many of the mega-successful young female stars feel they have to present themselves in a very over-sexualised way – even Beyonce.”

This is clearly something McIntosh, who also has two daughters Emer, 24, Georgia, 21, and is close to Caitlin, 28, Ross’s daughter from his previous marriage, feels strongly about.

“Beyonce shouldn’t have to do all that – she’s absolutely brilliant as she is,” she adds. “Yet more often than not in videos and on stage she leaves little to the imagination. I don’t know if I buy the whole 'freedom to exploit ourselves' argument used by some. It’s fine to be liberated and unafraid of sexuality. But why choose to go on stage and show your thighs every single time? Is that the only currency you’re going to deal in? There’s a real pressure on women to sell everything they’ve got and it’s much worse now than it was when we started out.”

One aspect of the music business McIntosh admits did get her down was the criticism of her musical contributions to the band. “Just another annoying girl ruining a good song with woo, woo, woo backing vocals” was one line from a well-respected music journal of the day. Much of the talk was sexist and condescending, of course, and it is notable that Wendy Smith of fellow 1980s band Prefab Sprout suffered a similar fate at the hands of the male-dominated music press. McIntosh admits it stung – a lot.

“I believed all that stuff,” she says. “After Real Gone Kid had been a hit I remember someone saying something about how amazing it was that I had made a whole career out of making train noise. Someone else said, ‘I’d love that song if she didn’t sing all over it’. I remember thinking maybe that’s right, maybe I do sing too much. Maybe I do sound awful.

“But time passes and you find more strength and confidence. Now when we’re playing live, Ricky and I are pretty much singing duets. Those two voices together, that’s what Deacon Blue is, no matter what you happen to think of it.

“The whole thing about being judged as a woman gets more interesting as you get older. ‘Is she ageing well? Should she be wearing that?' They’re not saying that about Ricky. But I’m strong enough to take that these days.”

I can’t help but think it’s remarkable that McIntosh was able to shake off the criticism and find her confidence at all, when you consider the sad and difficult start in life she experienced. Aged just 11 her Irish mother Sarah, a factory worker, died of leukaemia. Her father David, who also worked in a factory, struggled to cope with the loss and became an alcoholic. The situation spiralled and McIntosh and her two elder brothers were eventually left homeless.

“I really loved primary school but when my mum died our lives were turned upside down,” she explains matter-of-factly. “My brothers had gone to university and I was left at home with my dad. We were living in poverty and half the time I didn’t even make it to school – I left with no qualifications.

“It seems such an obvious thing to say but losing your mum when you’re 11 really is awful. You don’t know that at the time, of course, because you just get on with it. But looking back now and thinking about my own children …”

She trails off and you can see on her face how painful that thought is. I start to understand why McIntosh might be such an empathetic person.

“If my dad had coped it would have been very different but he didn’t, sadly,” she continues. “We were thrown out of our house just when I was finishing school so I came to Glasgow at 18 by necessity rather than as part of some plan. I slept on a mattress on my brother’s floor.” Her father died not long after Deacon Blue became successful.

Despite the emotional and financial hardship she undoubtedly suffered, McIntosh is remarkably accepting and upbeat about moving to Glasgow as a bereaved teenager.

“I didn’t feel worried or depressed,” she says. “I knew that all the bad stuff wasn’t my fault and I remember thinking, ‘Right, now my life is going to start’.”

Both McIntosh and her brother were keen singers and many of his friends were in bands.

“We lived in the crumbiest flat on Great Western Road and our lives were spent there with nothing but a record player and the latest Springsteen album if we could get our hands on it,” she smiles. “Music was my saviour. It was such a brilliant time. But that’s what life is when you’re young. And I suppose for all I missed the input of parents, I was also spared the expectations. I made my own way in life and looking back I had so much freedom.”

After going back to college to get her Highers and being accepting to study teaching, McIntosh met Ross, who was seven years her senior, while she was busking one of his songs in Buchanan Street.

She says the experiences of her young life have fed into her twin career as an actor, which began with a small part in the 1998 Ken Loach film My Name Is Joe, followed with a role as an alcoholic in the BBC Scotland soap River City.

“I’m fascinated by other people’s stories,” she explains. “I’m not saying I’ve had a worse time than anyone else, but it was what it was and you bring an understanding of your own life to every part. And since then I’ve had such a lucky life, such a happy life."

These days McIntosh is known for her accomplished theatre work with the likes of the National Theatre for Scotland, where she won praise for lead roles in Men Should Weep and Let The Right One In.

"Acting really helped me see that I could do something well," she explains. "Ricky and I were looking at a picture just yesterday of me in My Name Is Joe. He thought I was in my late 20s but I was 34, which is pretty late to get into acting. And I had no training. But I thought, I’m going to do this.

"The part that really made me realise I could hold my head up was Maggie in Men Should Weep. I remember the director saying to me, 'You’re so inexperienced I’m not sure you can carry this part. You’re only off-stage for about two minutes in the whole play'. I was so scared. But I put everything I had into it. I did it, and did it well, and after that run I really felt that I have proved something to myself and others."

And she is about to act in front of her biggest stage audience yet, in Still Game.

“I agreed to do the part because I’m a massive Still Game fan – it’s as simple as that,” McIntosh smiles. “You struggle to find anyone in this country who isn’t, of course. It’s a phenomenal piece of work.

“Jack and Victor are Scottish icons. Still Game is so true to itself and it never loses its heart. I think it harks back to a time when we weren’t always being fed the line that we need to buy better or bigger things, or achieve more, or be more successful. It takes us to a place of contentment. That’s why it’s so popular. And it’s one of the few things you can watch across the generations. Seamus won’t come through and watch a film with Ricky and me – but he’ll watch Still Game with us.”

In future, McIntosh would like to do Shakespeare, and her eyes light up when I suggest Lady Macbeth. Until then, she’s happy to be hanging out in Craiglang with Jack and Victor – though she still won’t let on who she is playing.

Still Game: Live 2 Bon Voyage is at the SSE Hydro from this Saturday until February 16. Tickets via www.thessehydro.com / 0844 395 4000