POSTNATAL EXPRESSION The difficult birth of Dear Frankie, a movie about a Greenock kid coming to terms with his parentage, prompted director Shona Auerbach and writer Andrea Gibb to reassess the role of modern fathers

Meanwhile Gibb, who wrote the original script as a 15-minute short when her own son was nine and her career was just beginning, matured into one of Scotland's most prolific screenwriters.

Initially, what brought the two women together was luck. Auerbach simply chanced upon Gibb's script; they had never actually met and didn't even live in the same country. What kept them together were shared interests and common life experiences, which gave them the determination to put Dear Frankie onto the big screen.

It was the emotion inherent in Gibb's script that first touched Auerbach. "If I'm really honest, it made me cry, " says the 37-year-old in her warm Warwickshire brogue. "If I was to analyse it, it was probably because of this woman's unconditional love for her son, the fact that you will go to any lengths - even if you're going about it the wrong way - because you love someone. I'm quite fascinated by that kind of passion."

She was also undergoing some life changes of her own, of course. "I was really broody at the time I first read the script and, bizarrely, it was around then that I got pregnant. I think as the years went by and I started to have children, I started to understand Lizzie."

Despite its simplicity, Dear Frankie's plot is morally complex. Lizzie pretends to Frankie that his father, Davey, is away at sea when in fact she left him years earlier for reasons that become clear as the film progresses. Lizzie writes her son letters purporting to be from Davey, complete with foreign stamps which Frankie glues into a scrapbook. When Frankie learns that the ship on which Davey is supposed to be serving is soon to dock in their hometown of Greenoch, Lizzie has to find a surrogate father who will pretend to be Davey for a day. Her friend recommends a man she knows; a man whose name we never learn. Frankie, by the way, is deaf.

Lizzie's feisty, chain-smoking mother makes up the third member of this curious family unit and her relationship with her daughter is alternately fond and truculent. Meanwhile Lizzie's hostile, businesslike relationship with the stranger softens. She begins to respond to him as a woman rather than as a concerned parent, which adds piquancy to the film's bittersweet conclusion.

But it's the relationship the stranger forms with Frankie himself that gives the story its emotional punch. What Gibb initially intended as an exploration of parenting from a single mother's perspective has turned into a questioning essay about fatherhood - indeed, at the film's various festival screenings it was the men who had tears in their eyes as the lights went up.

"The film seems to have hit male audiences, " Auerbach admits, adding that an "overwhelming" number of men have been moved by it. Gibb agrees. "I think the film is really about the male bond, " she says. "We often see projected a negative image of masculinity and fathers, but in fact it's really important for boys to see that there is a positive, constructive side to masculinity and I wanted to explore that."

But the film has other resonances for the writer and director. Like Frankie, 43-year-old Gibb was raised by her mother and grandmother above a chip shop in Greenock, where Dear Frankie was filmed. Her father was often absent, working overseas. Auerbach, who grew up in Warwickshire, lived for a time with her Scottish grandmother. Each woman has a childhood rooted in tiered, matriarchal households.

If Dear Frankie has a cinematic template it is Kolya, a Czech film from the mid-1990s in which an elderly musician becomes the accidental stepfather to a five-year-old boy. But Auerbach looks to eastern Europe in other ways too. After studying film in Manchester, she moved to Leeds to do an MA and spent her final year of that course studying at the Polish Film School in Lodz. The experience was eye-opening. "I think it was probably the most inspiring time I've ever had. It changed the way I look at film. It brought out a freedom in me."

Auerbach's style on Dear Frankie takes its inspiration from the techniques she absorbed in Poland and from that same sense of freedom. The result is a very visual sort of film-making, slow and deliberately photographic. Images rather than words become the tools of choice. To create her colour palette - muted browns and greens - Auerbach studied work of the Glasgow Boys and Girls.

"I thought they captured the light so beautifully, not necessarily in a romantic way but they show that there's a warmth to the light . . . What it did was what I had intended: get away from the film looking gritty and bring a warmth. It was important to me not to make it a gritty, tough film."

Interestingly, some critics have described her direction as "painterly". Is she related to Frank Auerbach, the German-born abstract painter who, like her own father, arrived in Britain as a Jewish refugee from Nazi Germany? "Who knows?" she laughs. "I did write to him when I was about 13 suggesting that we might be related and he wrote back to me, a very nice letter saying where his grandfather was from. But we just don't know. Somewhere down the line we might be."

For Auerbach, making this film was, in every sense, a family affair: her husband, Graeme Dunn, operated the camera. Andrea Gibb was fascinated by the way they worked together, apparently saying very little to each other.

"They'd be quite silent and incredibly calm and Shona would just sort of touch Graeme's back and he would move the camera very slightly, " she says. "They were symbiotic. It was like they were one person when they were working."

If the film's six-year gestation was vexing for its makers, the upside is that Dear Frankie hits our screens at a time when fatherhood is front-page news. The caped protesters of the Fathers 4 Justice campaign are becoming a regular feature in the headlines; former home secretary David Blunkett created a media storm over his attempt to establish paternity of his ex-mistress's son and expected baby; and last week Tory MP Ann Widdecombe published her second novel, Father Figure, about a teacher whose wife leaves him, taking their two young children. The novel follows his bid to maintain contact with his children while finding the law weighted against him.

Perhaps it's these topical themes that have given the film its strong commercial impetus.

Long before it was selected for screening in the prestigious Un Certain Regard section of last year's Cannes Film Festival, Dear Frankie had been picked up by Miramax, the US distribution company run by the legendary Harvey Weinstein.

Miramax executives saw an abbreviated version of the film at MIFED, a film industry trade show held in Milan, and bought it outright. Weinstein himself flew to London to view a final cut, and loved it. Although it has yet to open officially anywhere, it has already been sold to all the major territories and has won 12 awards at film festivals across Europe and North America.

It was the Cannes screening, however, that Auerbach and Gibb will never forget. "I don't think that trip will ever leave me, " says Auerbach.

"We got a standing ovation, 10 or 15 minutes.

There were hundredss of people there. It was very special and very overwhelming."

"They just started to clap, " recalls Gibb, "and the clapping just kept going. We thought it was a bit odd so we turned round and they were all just hanging over the balcony at the top shouting 'Bravo! Bravo!' People said I looked like I'd been hit on the head by a hammer."

That warmth was not extended by the critics.

Dear Frankie may be a proven audience-pleaser but its emotional content has laid it open to claims of sentimentality and, although Gibb contends that the reviews have been mixed, Auerbach admits it isn't a critic's film. But she doesn't sound too bothered. There is, she says, a line between the emotional and the sentimental and she is not a sentimental director. "I think anything with emotion in it is at risk of stepping over that line. It's quite hard to go up to that line and not step over it. But I hope I haven't."

Right now, Auerbach is back in the world of TV commercials where she has carved a name for herself as an innovative director on campaigns for Nescafe, Whiskas and Domestos. She isn't fazed by the occasional snobbish comment from the denizens of the film world: commercials pay the mortgage and allow her to live in Warwickshire with her family. But there are other cinematic projects bubbling away, predominantly an American-set film with a script written by a longlost cousin she encountered in San Francisco two years ago, and another that she characterises as "a tragic love story". She also has a trilogy up her sleeve, and is not short of ambition. So which film will we see first? "Who knows?" she laughs. "I'm juggling them all at the moment - and trying to be a good mum at the same time."

Meanwhile Gibb is working on a number of other screenplays, including an adaptation of Louise Welsh's novel, The Cutting Room, starring Robert Carlyle. But she doesn't discount working with Auerbach again. Like Ken Loach's film, Sweet Sixteen, Dear Frankie was shot in Gibb's hometown of Greenock. I suggest she may become the Paul Laverty to Auerbach's Ken Loach, producing dreamy fables where that writer/director team concentrates on gritty dramas. She laughs, but I sense that she quite likes the idea.

What she does plan to do is pay her money and go watch Dear Frankie in a Greenock cinema. "It opens in the Waterfront on Friday and I'm thinking I might take my mum and dad there, then see what the locals think of it."