You walk down a grim alley, peering through smeary, red-lit windows at 11 “girls”: their bodies are plaster casts, their heads poached from shop dummies and encased in glass-fronted boxes. One washes her crotch at the sink; another in fur coat and boots waits in the street; a blonde with her arms folded has harshly glamorous make-up and a black triangle of pubic hair under her clinging nylon knickers. Their bedrooms are cubbyholes with leopardprint wallpaper, and, outside, the Dutch everyday of parked bicycles. The scene has been haphazardly slopped over with a thick resin that dribbles down the girls’ hair and faces like horrible sap.

But you’re not anywhere seedy — well not conventionally so. The Hoerengracht, or “Whore's Canal”, is the National Gallery’s feather-ruffling new show: an installation reproducing full-scale a section of the red-light district in Amsterdam, by the American artists Ed and Nancy Kienholz. Until Ed’s death in 1994 the husband and wife team specialised in bric-a-brac assemblages of flea-market detritus, queasy side-show freaks and blunt, moralistic satire.

The exhibition is timely. Last month Ian McShane, MP, and Nikki Adams of the English Collective of Prostitutes scrapped on Newsnight over a failed police operation against sex trafficking. Contradictory statistics have been flying: are there 25,000 trafficked sex slaves in the UK, or a handful? Nicholas Penny, director of the National Gallery, isn’t known for his love of sensational, headline-grabbing exhibitions, so how did this one get through?

The Kienholz piece was championed by Colin Wiggins, the gallery’s acting head of education. “The British are so prissy, so safe and tame and tasteful,” Wiggins says. “Kienholz communicates without an art historian having to come along and explain it. It smacks you in the stomach.” He chose The Hoerengracht because its windows, light and vistas remind him of the gallery’s Dutch Old Masters on the same theme, which will show alongside the Kienholz girls. For Penny’s part, he thinks that The Hoerengracht is not a condemnation of prostitutes themselves, but that “it certainly doesn't glamourise or romanticise prostitutes. It wasn't made as a warning. But if you are a crusader against prostitution you’d probably have to welcome it,” he says. “It’s meant to provoke strong reactions.”

Nancy Reddin was a photographer when she met the artist Ed Kienholz in 1972, and they began collaborating. They worked on The Hoerengracht in their Berlin apartment for five years from 1983. “It took over,” Reddin-Kienholz recalls. “We were living in it. We worked on it for five years and I’d say to Ed: ‘Pimps and whores, pimps and whores, I’m so sick of pimps and whores!’.”

Reddin-Kienholz is adamant that The Hoerengracht had an ideology-free conception, despite the artists’ reputation for polemical work. “The whole time we worked on that piece I really didn’t think much about prostitution,” she says. “I was making whores but I didn’t think about it because I was doing it from an aesthetic point of view. The idea was purely from Amsterdam, because of the light; the girls used black light and red light, and they looked fantastic. We were there looking at the architecture, the interior of the rooms, not the girls.” Ed Kienholz, however, had done an earlier brothel installation on his own in the 1960s (on display at El Sourdog Hex gallery in Berlin from Saturday). Roxy’s is a far more nightmarish and politicised work. The madam has a boar’s skull for a head and the girls are dismembered, or made out of rubbish bins and bedpans.

If The Hoerengracht does have an ideological angle, Reddin-Kienholz says, it is: “Why lie about it? Why pretend [prostitution] isn’t going to exist? The only thing you do is put it underground and make it less safe for everybody. Less safe for the girls, less safe for the men, less safe for the community. It’s going for legalisation, because I don’t think it’s a sin. I believe that having open brothels is much safer for your mother, your sister, your daughter, because it’s available. I think you have fewer rapes.”

Of the glass frames round the women’s heads, she explains: “They’re under the control of the women. She can control her own emotions and cut herself off.”

The famous Dutch tolerance was supposed to encourage this — detached businesswomen in a pimp-free Utopia, choosing their clients and giving a cut only to the taxman, but the transition to legalisation in De Wallen, the Amsterdam district that inspired the piece, has not gone so smoothly. Sarah Forsyth, a British woman, published a harrowing memoir, Slave Girl, which told of her time as a trafficked, addicted prostitute in 1990s Amsterdam, in which she witnessed another girl killed for a snuff movie.

The Hoerengracht girls are not threedimensional personalities, with children to feed and boyfriends who love them; they don’t have hearts of gold, their choices and backstory remain enigmatic. But their presence, and the setting of the exhibition, will sharpen debate: some will find them grotesque, unpleasant, stomach-turning even, but they’re defiantly present. They are neither victims nor happy hookers, and here they are at the centre of cultural London — for the school groups, the tourists, the art goers — right alongside the Old Masters.

Kienholz: The Hoerengracht is at the National Gallery (www.nationalgallery.org.uk), Nov 18-Feb 21

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