It’s mid-afternoon and Ken Loach shuffles into Studio 3 of a Soho postproduction facility. Dressed in a denim shirt, he’s come to record the DVD commentary for his latest film, It’s a Free World, a powerful indictment of the exploitation of migrant workers in modern Britain. “Is it the usual thing?” he says, in his softly spoken voice, to the engineer. “Just burble away and stop if it gets boring?” This self-deprecating comment is typical Loach: at 71, he’s still a man whose manner is as modest and unassuming as his work is polemical.

Later on, he refers to his 2006 film, The Wind that Shakes the Barley, which recounted the bloody history of British imperialism in Ireland, as a work that “did quite well in Cannes”. It actually won the Palme d’Or, a first for Loach. “It was just a nice seal of approval,” he says. “But it was particularly good to get [it] for that film, since we were so attacked in the right-wing press.” Among many critics, Simon Heffer of The Daily Telegraph declared that he had not seen the film and did not need to, “any more than I need to read Mein Kampf to know what a louse Hitler was”.

But Loach has become used to such criticism in his 40-year career. Hidden Agenda in 1990, which dealt with covert British operations in contemporary Ireland, was regarded with similar distaste by Tory MPs, who accused it of being pro-IRA.

Despite Loach’s triumph in Cannes, The Wind that Shakes the Barley trickled out on only 40 prints in the UK – compared with 350 in France – so it’s no surprise that It’s a Free World will take a different route. Like his 2001 railway worker drama The Navigators, the film will go direct to DVD after a showing on Channel 4. “It’s quite good every few years to do one on the TV because we get a much bigger audience,” he says. Also being released this month are two box-sets, each with eight films.

If Britain is grudgingly acknowledging one of its finest film-makers, then perhaps it’s in recognition of a burst of creativity. After a barren spell in the 1980s, when funding for socially conscious cinema was nonexistent, Loach has made 13 films since 1990. He has found a like mind in the Glaswegian screenwriter Paul Laverty, who has written almost everything Loach has directed since 1996’s Carla’s Song.

Loach’s work often views events through the eyes of the downtrodden but not so in It’s a Free World. “We felt it was maybe a bit obvious if we did the story from the point of view of the exploited workers yet again,” says Loach. “We wanted to do the film from the point of view of someone who did the exploiting.” Thus, the film’s main protagonist is Angie (the newcomer Kierston Wareing), a brassy lass who sets up a recruitment agency to provide cheap illegal workers to London businesses. It is shot in Loach’s trademark manner – the actors are never shown a complete script to keep the performances spontaneous.

Loach’s upbringing was hardly radical. He was brought up in Nuneaton, Warwickshire, where his father was an electrician. He was “nonpolitical and a Daily Express reader”, says Loach dryly. After two years in the RAF, Loach studied law at Oxford but spent most of his time putting on plays. After joining the Northampton Rep Theatre in 1961, Loach met his wife Lesley, with whom he’s had five children (one died in a road accident in 1971). He joined the BBC and in 1966 his drama about the homeless, Cathy Come Home, had such an impact it led to the formation of the charity group Shelter.

Disillusioned by the Wilson Government, Loach’s left-wing beliefs were focused. “If you’ve been through that kind of education [I had], you have an obligation to deal with things,” he says. In 2004, he joined George Galloway’s Respect party, even standing in a no-hope seat in the European elections. He feels that the Labour Party has abandoned the Left, and is not optimistic about Gordon Brown (“He’s absolutely antiunion.”).

Loach’s next task is a documentary for Channel 4 on the trade unions. Britain is witnessing the destruction of “the organisations that defended mutual support, respect for each other, solidarity, decent wages and decent conditions,” says Loach. Everything, in fact, that he stands for.

It’s a Free World, Sept 24, Channel 4, 9pm. It is released on DVD on Oct 1

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