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Steven Soderbergh made his name as a director with his first film, sex, lies and videotape. He has gone on to win an Oscar for Traffic, but 20 years after his debut, he has returned to familiar territory with a film that could just as easily have been called sex, lies and the internet.

The Girlfriend Experience, a kind of art-house Secret Diary of a Call Girl, is about a week in the life of a $2,000-an-hour New York “escort”. It was made last October in the aftermath of the downfall of Elliot Spitzer, then governor of New York, who was forced to resign after being caught up in a high-class prostitution ring. An unfinished version of the film screened at the Sundance festival earlier this year; it premieres at the Tribeca festival, in New York, on Tuesday. “It’s a subject I’ve been totally interested in since the beginning of my career,” Soderbergh says. “This is a milieu I’ve never explored before.”

Between the two films bookending Soderbergh’s work, the world has changed, along with the format. sex, lies and videotape, in which James Spader’s character has to revive his libido by interviewing women about their sex lives while filming them, was about the distance between love, intimacy and sex, and the lies that are told because of it.

Two decades on, sex has been widely commodified. Prostitutes openly advertise their services and fees on slickly designed websites, and hardcore pornography is never more than a couple of clicks of a mouse away. In this world, the “girlfriend experience” is the pretence of intimacy some escorts offer and their customers pay extra for, including kissing and what may even pass for friendship. As one reviewer noted: “Soderbergh borrows one of Jean-Luc Godard’s favorite themes — prostitution as a metaphor for capitalism — and adapts it to an America in which the line between selling out and selling yourself has never been thinner.”

The film was shot — for only $1.7m — in 16 days, in a surprisingly sumptuous style, full of reflections and surfaces. It opens with the escort, Chelsea, on a “date” with a man who appears to be her boyfriend, but turns out to be one of her clients. We see her meeting a financial adviser and a sleazy internet reviewer of prostitutes, as well as her boyfriend, a trainer in a gym. While Soderbergh was shooting, the Wall Street he was depicting was having its last hurrah, a world where rich young brokers fly to Las Vegas in a private plane to spend time with high-class prostitutes while they fret about the stock-market crash.

Yet Soderbergh is nothing if not contrary. His first film dangled a teaser title before the audience, but showed little actual sex; The Girlfriend Experience features none, just one brief nude shot of its star, Sasha Grey, who plays Chelsea. Which is particularly intriguing — and deliberately so — because Grey, who was 20 when the film was shot, is one of the most notorious porn stars in the world. (All the other “actors” are nonprofessionals.) Soderbergh says he chose her because, like her character, she makes a good living selling sex and the fantasies surrounding sex. Since she started working in “adult entertainment” when she was just 18, Grey has made more than 150 porn films.

“Even though the film’s not very explicit,” Soderbergh says, “there’s a comfort level she obviously has from making all of those films that I think is difficult to fake. There’s a kind of attitude.” It’s an attitude of unnervingly unknowable blankness that works perfectly for her character.

Soderbergh clearly enjoys toying with the tension of our expectations, but there is an even more interesting subtextual tension in the choice of a top porn actress to star in an art-house movie directed by an Oscar-winner. It begs important questions. Pornography may now be pervasive, but how acceptable is it in mainstream culture today, how acceptable should it be, and how do we really feel about those who perform in it?

For Grey, those are not academic questions. She’s made it clear she hopes for a career beyond porn, something that has eluded most other actresses who have tried, including Marilyn Chambers, the star of the influential 1972 porn movie Behind the Green Door, who died recently at 56, penniless. “I’ve got to diversify myself,” Grey says. “Do I want to be 35, having sex on camera? No. I want to be sitting on a porch at my beach house with my own successful company.”

The question of mainstream acceptability is even more tricky, in Grey’s case, because of what she represents in pornography. The publicity material for The Girlfriend Experience portrays her as “an American actor, writer, photographer, porn star, transgressive artist and experimental musician. She declares a strong interest in the films of the French new wave and, before deciding on her present stage name, toyed with the name of Jean-Luc Godard’s ex-wife, Anna Karina”. This is no common or garden porn star. And if you take yourself to Grey’s MySpace page, what awaits in the list of what she likes is a compendium of the avant-garde and intellectually challenging: directors such as Antonioni, Bertolucci and Lars von Trier; writers such as Burroughs, Yeats, Baudrillard and Nietzsche; artists such as Donald Judd. Her occupation is described as “existentialist, porn star and artist”.

Maybe she’s serious, but this attempt at putting a high gloss on what she does for a living may not convince everybody. For Grey will find it hard to distract people from her tastes in pornography. Her appeal comes from the unholy collision between her youth and apparent physical innocence — she is petite, pale and small-breasted — and the extraordinarily extreme, violent and degrading acts to which she is subjected. Apart from what are now standard pornography tropes of rough sex and violent gangbangs, Grey is routinely abused and degraded in almost every conceivable and inconceivable way — to her apparent satisfaction. The only acts she will not undertake, she says, are those involving children or animals.

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