There is a phrase Ken Loach uses constantly when describing his films: "authenticity of experience". He has always been more interested in telling stories about real people's dilemmas and experiences than in flashy camerawork, special effects or "style" for its own sake. He works on location, with pared-down crews. Nobody is allowed on set who doesn't have a specific job to do, and actors are told only as much about their roles as their characters would know. As playwright Trevor Griffiths once noted of him, he's the kind of director who "would shoot without a camera if he could".

On the face of it, that makes his decision to direct in the US for the first time a surprising one. "When we make films with Ken, we have our own particular way of doing them," says producer Rebecca O'Brien. "We don't need to have the whole circus that is the Hollywood film unit. To be able to get to the level of realism [Loach wants], you need to have as little clutter around you as possible."

By a neat quirk of irony, Loach risked falling foul of the American film unions' stipulations on manning levels. The budget for Bread And Roses was $5.5 million, generous by Loach's normal standards but peanuts by Hollywood's. The shooting schedule was whittled down to 30 days to keep the cost down. "We couldn't afford to be there any longer," says O'Brien, whose only previous experience in LA was working on Bean in 1997. "Quite a few people just thought we were taking the piss. The Screen Actors' Guild and The Directors' Guild have low-budget rates. We negotiated to come under those agreements, and that was fine. But SAG couldn't believe we could have real people in our films in the quantity that we have."

The storyline was inspired by the Justice For Janitors campaign, a drive to win employment rights and better pay for cleaners and janitors that is still in progress across America. The film was scripted by former human rights lawyer Paul Laverty, writer of Carla's Song and My Name Is Joe, who had been on a writing scholarship in LA ­ where most of these workers are Latin-American immigrants. Laverty met some of the cleaners involved in the campaign and he knew that theirs was the kind of story that might appeal to Loach. But it took several years to develop the screenplay ­ labour disputes, as Laverty acknowledges, don't necessarily make for great drama.

Nor could Laverty claim to know the cleaners' world from the inside. "It's a great mistake to lump them together," he says. "While characters might be cleaners and speak Spanish, the experiences of a Guatemalan peasant or an ex-combatant from El Salvador or someone from a shanty town on the outskirts of Mexico City are worlds apart."

US distributors, initially eager to pre-buy Bread And Roses, shied away from the project when they realised how much of it was Spanish-language. "That's the language of the film," notes O'Brien, who felt it would have been absurd to shoot the film entirely in English simply to please potential American backers. "The Latino workers speak to themselves in Spanish." Similarly, Loach avoids the usual visual clichés of Los Angeles as a city full of cops, freeways and movie stars. "We wanted to wipe the mist from the window and see real people there," he explains.

The film, largely set in downtown LA's business area, follows Maya (Pilar Padilla), a new arrival in LA from Mexico who becomes involved in the janitors' campaign. Like many others in the Latin immigrant community, she is working in a badly paid job with no rights, but if she complains, she runs the risk of being sacked and even deported.

Casting was exhaustive. Loach saw hundreds of actresses before finally choosing Padilla, a theatre actress he found in Mexico. Padilla didn't speak English and didn't know the US well. In other words, her background was much closer to that of Maya than those of many of the LA-based actresses Loach auditioned for the role. Padilla is cast alongside a mixture of newcomers and well-known faces: Adrien Brody (The Thin Red Line, Summer Of Sam) plays union activist Sam, while Elpidia Carrillo (Salvador, The Border) plays Maya's older sister, Rosa.

A number of union organisers active in the Justice For Janitors' campaign also have roles in the film, but O'Brien denies that the janitors were ever in any way suspicious of finding a British film crew in their backyard. "I think they were delighted," he says. "Nobody else was telling it from there. There wasn't anybody from Hollywood coming five minutes down the road to tell their story."

Geoffrey Macnab