Katy Guest: Meryl's boob beats Keira's tum. Hands down

Instead of a fleeting flash of breast, this is nudity on a slab

On the cinephile website Celebrity Nudity Database a movie fan reviews Meryl Streep's 1983 film Silkwood. "Streep, as Karen Silkwood, flashes a tit at a co-worker and exposes the top half of her left breast," writes BFDMan, charmingly. "I have given it an extra star simply for being that stuck-up Meryl Streep." The generous addition takes her nudity rating to a full two stars.

It is not among Streep's better reviews. Her biography on the otherwise unimpressionable Internet Movie Database reveals matter-of-factly that she is "considered by many movie reviewers to be the greatest living film actress". She has been nominated for 13 Academy Awards and won two. And she could act most rivals off the stage using her cheekbones alone.

Which is why it seems a little mean for Meryl Streep to be picking on those smaller than her. At the Berlin Film Festival last week, Streep criticised the young actresses Scarlett Johansson and Keira Knightley for appearing naked in Vanity Fair. "They obviously feel that to emerge from the pack they have to distinguish themselves by being more willing to do that than anyone else," she said, pityingly. "It's not about the roles they aspire to - it's that they have to sexualise themselves."

If Streep is turned off by the Vanity Fair shoot, she has a point. On the cover, Knightley poses smugly with an expression that says simply: "I'm thin. You're not." Johansson sprawls beside her like a sulky little sister. And the hairy-chested Tom Ford leans in proprietorially, his coolly raised eyebrow calling for male readers to ask themselves, not for the first time, why it is that gay men get all the best chicks.

But something about it is just not very sexy. Instead of a fleeting, two-frame flash of breast, the suggestion of a buttock, this is nudity on a slab. We can scrutinise Keira's scrawny tummy, and examine the oddly unflattering angle of Scarlett's thigh. The pictures will be admired and dissected, pored over and picked at, but they will not be searched for hotly through thickets of websites, nor pinned like a rare butterfly to the pages of celebritynuditydatabase.com. Not like that half-second flash of Meryl's left breast.

Other actresses were right when they decided to embrace nudity in their movies. Christina Ricci talked of it being "liberating". Diana Rigg carried on womanfully, even after a nude scene in the 1971 play Abelard and Heloise led to her being described as "built like a brick basilica with too few flying buttresses". Diane Keaton found her experience of it so positive that the announced (if not entirely seriously), "I'm always going to do nudity in my movies. I'm going to insist on it in all my contracts."

Helen Mirren sometimes seems to have done exactly that. Surely one of the most brilliant - and least "sexualised" - moments in movie history was when she stood behind two currant cakes in Calendar Girls and announced cheerfully: "We're going to need considerably bigger buns".

Rather than getting her sensible knickers in a twist about decent, honest nudity, Streep should complain about the insidious suggestiveness that seems to have permeated prime-time TV. What is really offensive is Pat and Patrick in EastEnders making sly insinuations about whipped cream and pineapple rings. It is adverts for smoothies that ask, "Are you getting enough?" It is anything that compares a low-fat yoghurt to making love.

Because it is dark and clandestine, Meryl Streep's freeze-frame glimpse of tit is far more sexualised than the flesh on offer in Vanity Fair. She should overcome her barriers and try feeling the wind on her nipples. Then she could reasonably expect to win at least three stars.