I'm going to be rude about this show. However, it's worth recalling that just 10 years ago the Serpentine Gallery put on the Rego exhibition, launching her remarkable, late career. It was a startling breakthrough - the artist was already 50. What's more, the paintings that made such a stir, did so by utterly disregarding one of the most unbreakable protocols of modern art - the ban of the "anecdotal". They sold stories, and believed them.
True, a revival of figurative and narrative painting was widely touted in the 1980s. No one, though, was on the look-out for anything so whole- hearted. These scenes of family sex dramas took their tales seriously. It wasn't a question of interesting imagery - the viewer was asked to identify directly with Rego's characters, imagine their lives and feelings, as if they were people in a novel. That was how the pictures worked. Old-fashioned, and perhaps even naive, but it is evidently one of the ways pictures can work, and it was done with irresistible conviction.
Story is Rego's forte. Each new show has told a new one, presenting a new cast of characters. In the last few years, for instance, we've seen The Dog Woman and The Ostrich Women - both convincing developments of Rego's basic plot; an ambivalent one of female survival, cunning, secrets, resistance and revenge, all qualified by a deep emotional investment in subjection and victimhood. Her fables are always woman-centred, but I've never understood why she's called a feminist artist. Men may appear in her pictures as passive toys, but there is always an offstage context of invincible male power. Liberation and equality aren't her business at all.
The 16 large pastel compositions showing in Dulwich are based on a book, The Sin of Father Amaro, by Eca de Queiros - a 19th century Portuguese novel which, probably like many viewers, I haven't read. But then Rego's pictures are not literal illustrations. So it is hard to tell whether knowledge of the text would enrich or encumber them. Anyway, visitors get a printed precis of a woman seduced by her priest-confessor, and it's a world of passion, guilt, sacrifice and gender segregation - in keeping with Rego's world as we know it.
Except where are the stories? The Ambassador of Jesus is the only image in this set with one of Rego's distinctively charged actions. A priest sits facing a woman, one hand held out with holy fervour, clutching her head in benediction; the other, as if this too were part of a ritual, clutches her thigh. His eyes are raised to heaven; she doesn't look quite sure. It's not an original scenario, but it whets the appetite for more.
In vain. None of the other Father Amaro pictures have this level of drama. Rather, there's a great deal of sitting and lying around, with sometimes just a hint of some gesture or expression, but nothing telling, and a scattering of symbolic props - dead chicken, dolls, minature pig - to make up for the lack of action. This is artistically risky. Without the one thing Rego's very good at, you're likely to notice the various things she's not good at.
These pictures do little to disguise the way they're figure compositions set up in a studio - in fact, they deliberately stress this. They don't show period scenes, but models enacting period scenes, half-dressing up in costumes or in modern dress, and with modern furniture. There's the odd alienation effect, too: in The Company of Women, a scene from Amaro's childhood, he's played by the same man who plays him as an adult. I don't think this studio charade is such a great idea in itself. It can only further weaken narrative interest. Worse, it is exposing. Studio-bound life work is not Rego's forte, and the competition (to give it a name, Lucien Freud) is stiff.
Those striking images Rego was making 10 years ago - the girl polishing the father's boot, say - were, I guess, mainly from imagination. The figures were cartoony, but they had psychological vim. Later, she began to work from live models, probably to make things feel more grown up, less whimsical. And in the 1994 Dog Woman series, it was crucial. You needed to feel it was an actual woman living this dog's life - a made-up body wouldn't have done - and maybe just because a strange bodily life was the central subject of the story, Rego's drawing-in of those images was both physically and psychologically true.
But here, her anatomies are just like anyone's variably wonky life drawings. "Mistakes", as such, may not matter (though there are some eye-catchingly clumsy ones), but the general loss of force or particularity of gesture does, for that is her essential genius. It snaps in just occasionally - in the intently kneeling figure in a painting called The Rest of the Flight into Egypt. Elsewhere, you feel its absence keenly. For as straight depictions of flesh and bone, or arrangements of bodies and furniture, these images have very little in their favour.
No one ever went to a Rego picture for the rendering of textures and it's unfortunate that clothes and materials make so much of the going- on in these pictures, at least in terms of picture area filled, promising a sensuous drama of black silk, white lace, carpets and bedding that never materialises. In Looking Out, a woman gazes out of a window, the swirl of drapery around her hefty bottom being (as it ought to be) one of the main pictorial points. But - to put it mildly - to show this picture in a gallery which has Van Dycks in the room next door is optimistic. The colours are pretty dull, too.
To put it less mildly, about a third of these pictures simply shouldn't have been exhibited at all, and without Rego's good name, I can't imagine they would have been. The rest distantly remind you of what Rego has done so much more powerfully before. Something has gone very badly wrong here. I hope it is nothing more serious than a total lack of interest in the project in hand. But don't rush for a seat on the coach.
Dulwich Picture Gallery, London SE21 (0181-693 8000), until 26 July