Sarah Sands: It's not being 44 that is Demi Moore's problem

Despite her expensively preserved beauty, Demi Moore, 44, complains that acting parts are drying up. "There aren't that many roles for women over 40," she said last week. "A lot of them don't have much substance other than being someone's mother or wife." Thus, she writes off Lady Macbeth, Mother Courage, Hedda Gabler and Medea. Also, the timing of her complaint is clumsy. Michelle Pfeiffer is glorious in her latest film, Stardust, playing a several-hundred-year- old witch.

Meanwhile, our most celebrated British actresses, apart from Keira Knightley, are Judi Dench and Helen Mirren, both of them pensioners. They radiate energy and humour in a way that Moore emphatically does not. This could be because they are comfortable in their own skin – rather than somebody else's.

Moore may appear to be the greater feminist, denouncing the youth obsessed industry of Hollywood but she has bound herself to its rules. Like Sharon Stone, aged 49, who has also railed against ageism in films, her sales pitch is that she has not given a physical inch. Stone even made a sequel of Basic Instinct to show that she was as hot as everyone remembered her.

A Paris-based cosmetic surgeon once defined for me the difference between American and European faces. She said that American cosmetic surgery aimed to emulate the face of a 20-year-old. The skin was stretched as tightly as it could go. In France, older women preferred to look good for their own age. The example of contrasting cultural surgery she used was Faye Dunaway versus Catherine Deneuve.

Moore could reasonably argue that men have a longer shelf life for romantic or powerful roles. Why do women have to resort, like Pfeiffer, to self-mockery? Yet comedy is the greatest sign of humanity and understanding. Robert De Niro appears in Stardust wearing a tutu. There is a contented actor.

Moore is right that there are fewer great female roles than male ones. It is why Elizabeth I (currently being played by Cate Blanchett) and Joan of Arc (currently acted by Ann-Marie Duff at the National Theatre) are revived so often. The reason is partly a historical reflection of the public role of women.

We will not correct this through aggrieved actresses, however. The power does not lie with them. We need more women writers and producers and studio bosses. Dench was nominated for an Oscar for her performance in Notes on a Scandal, written by Zoe Heller. The reason that Tom Cruise or Harrison Ford get such good parts is that they have industry clout.

Moore has no influence on the kind of films being made, and they are currently unsympathetic to her. There is a great appetite for war movies and thrillers. The Bourne Ultimatum runs on adrenaline. There are no characters to mention, and the female parts are shockingly thin. Even Atonement is biased towards the male narrative. And when women are dominant, they are also painfully dull.

Maybe film actresses should take greater risks with their choice of parts. There is a self-congratulatory air about their hankering after liberal heroines such as Mariane Pearl. Wonderful woman, rather boring performance by Angelina Jolie. Mirren broke free by playing someone she had previously despised, who was the Queen.

Moore seeks the vindication of the discarded by associating herself with a grander cause. It is she rather than Jodi Foster, or Julianne Moore, who cannot get the middle-years parts. Has it crossed her mind that she is the lesser actress?