Kate Winslet's opening answers don't indicate a full and frank conversation is likely. "No and no," she says with emphatic brevity, dealing with the prospect of a career as a singer, and of making an album following her top ten chart success.

Short, sharp replies are not typical of this British actress who, since first attracting public attention in Sense And Sensibility, has conducted an open relationship with the press that makes you feel as though you know everything about her.

We've seen her through romance and marriage, awards and weight loss, pregnancy and divorce. While others retreat behind closed doors at the merest hint of a front page story, Winslet has steadfastly refused to follow that line.

When she split from husband Jim Threapleton, she left the house as normal with baby Mia, despite the press photographers waiting outside. When she found a new beau, director Sam Mendes, they went public at a film premiere, rather than sneak around denying romance. Even when she went on a diet, we knew all about it.

Inevitably, she was criticised by some for sharing her life and daring to have an opinion. But in these days of mass-produced, image-controlled celebrities, Winslet is refreshing in refusing to be anything but herself.

"When I felt invaded, I carried on as normal, especially now I have Mia. The press have never barricaded me into my own home," she says.

"There's been a lot of press attention and I'm probably followed if I take Mia for a walk. I try to ignore it and not let it get to me. I have a child and that's all that matters. You just sort of get on with it."

Her reluctance to discuss a singing career stems from an unwillingness to air her voice in the first place. The makers of A Christmas Carol, a cartoon film for which she provided one of the voices, asked if she'd like to sing a ballad written for her character. She said yes, and EMI were so pleased with the result that they wanted to release the number as a Christmas single.

"I said, 'no way' although I was happy to be part of the soundtrack," recalls Winslet. "They kept on and I said all right, as long as it was a charity thing."

She also sings in her latest film Iris, the love story of writer Iris Murdoch and husband John Bayley. Judi Dench is the older Iris, with Winslet as the young writer, a role for which she's up for a best supporting actress Oscar next month.

The song is performed in a pub. "I was naturally very nervous about it," recalls Winslet. "It was a poignant song that her mother had taught her. Judi knew it too. Here was me, the only one who didn't know the song. It was nerve-racking but I'm pleased to say the version of me singing in the pub was the one used. We didn't have to record it again."

The actress also spends much time in the water, something you think she'd want to avoid after making Titanic. But she relished the swimming scenes. "I do love water and always have done. I've always been a swimmer. As a kid, I was first in the water when we went to the seaside," she says. "We shot the scenes in a heated tank at Pinewood Studios. I was happy and didn't want to come out at all."

Winslet laughs at the mention of her stripping off again in Iris to go swimming in the nude. "If anyone is used to taking their clothes off it's me," she says. "You never get used to nudity, or enjoy or look forward to it, but this was something very key in Iris and John's relationship. They would go swimming all the time, and when they were young did a lot of skinny-dipping. So I never had a problem with it."

Mention of nudity inevitably leads to the subject of weight and her body being a subject of scrutiny since she became famous. Daughter Mia was barely six months old when she filmed Iris, and she hadn't yet regained her figure.

"It wasn't easy but I got there in the end," she says. "I didn't panic and think, 'oh god, I've lost my figure forever'. Now I've got back to the weight I was before I had Mia."

The chance to appear in Iris was so tempting - "when you're asked to play the young Judi Dench you don't under any circumstances say no" - that she ended a year-long break from acting after the birth of Mia.

"It was a short four-week shoot so I didn't feel I was away from her. In the first year of her life I didn't want to work that much," says Winslet.

"I've done two films but only worked 11 weeks - and she came with me both times. Actors are so lucky when we go to work that we can bring baby with us.

"I'm so present in her life. I'm never not there for enormous periods of time. I'm probably around a lot more than most working mothers. She's an incredibly happy little thing."

Her attitude to work hasn't changed. She never thought having a baby would mark the end of her career. "Had I worked at a ridiculous pace before, it would have changed. But before Mia I was only doing one film a year, taking up three or four months. As an actor, it's terribly important to take breaks. I've never chosen to work back to back."

Since Titanic, Winslet has opted for smaller films, including Quills and Enigma, rather than large budget projects. "I've not turned down blockbusters because they were blockbusters. I've just ended up doing things I'm passionate about," she says.

"The only really specific choice was Hideous Kinky. After Titanic, I wanted to d something British and small because I wanted to be mindful I was a young, British actress. I didn't want people to think I would dance off to America and work over there. British film is very important to me and remains so. Hideous Kinky brought me back to my roots."

She'll next be seen in Alan Parker's The Life Of David Gale, a contemporary American story ("I'm running around wearing jeans as opposed to corsets"). After that, who knows? "At the moment, I'm at home being a full-time mum and loving that. I'm reading scripts and will simply wait until something comes along that lights a little fire, and then go back to work."

* Iris (15) is showing in cinemas now.