Lloyd Newson doesn’t set out to offend. But try as he might, the director-choreographer can’t button that lip.

His latest show, To Be Straight With You, arrives at the National Theatre next week and marches onto the faultlines between tolerance and hatred, religion and sexuality. The research included a visit to the Lambeth Conference, where Newson got into heated discussion with an evangelical who was “huffing and puffing” that the Aids virus proved that God condemned homosexuality. At which point, Newson suggested that, given the negligible incidence of HIV among women who love women, perhaps God was a lesbian?

It probably wasn’t the first time that Newson’s blood was up and his mouth ran away with him. Although he keeps his steel-grey eyes on the table for much of our conversation, he’s an instinctive contrarian. Though he admits that at Lambeth, “generally, we were there to hear other people’s opinions. I was always aware that I shouldn’t get too emotionally caught up in what people wanted to say”.

It wasn’t merely committed Christians who roused his ire – he also asked an Islamic preacher how his views might compare to Hitler’s.

His Australian-accented voice is considered, his manner is quiet, but there’s no mistaking his indignant energy. Luckily, the project engaged two professional researchers, including the BBC-trained Anshu Rastogi who conducted, with Newson, the interviews which form the production’s core. It took six months to find enough people willing to share their experiences of homophobia in Britain’s religious communities. Particularly fearful were those who had been alienated from family or whose lives had been threatened, others whose sexual secrets remain firmly under wraps.

Occasionally, movement provided an instant key to character. They found a married man giving his best Bollywood in a gay Asian club – the researcher won his trust by getting on the dancefloor and shimmying alongside him. Dance allowed him to express a covert but fundamental truth about his life: Newson insists that he really was boogying to Shakira’s Hips Don’t Lie. “What’s fantastic about this piece is that it’s real.”

Those real stories are at the heart of To Be Straight With You, which is a piece of verbatim theatre. Edited interviews play through earpieces in performance, so that actors inhabit someone’s actual rhythm and inflections. Newson’s cast wore iPods while developing the show, “like clairvoyants, what they heard they had to speak”.

The show demands a scrupulous attention to text and a responsibility to the people who have disclosed deeply personal experiences: “We were constantly playing it [the recording] to each other to keep some level of objectivity. I was very concerned with nuances of language.”

If the work sounds like agit-prop, its impact is likely to be far more complicated, because Newson’s true gift is for poetic images which bounce people’s stated intentions against their aching hearts.

“If I could pay someone to follow someone for a week, I’d learn far more about them than from all their words,” he considers. “We all have our spin.”

Finding the soul behind the spin was the next stage of the rehearsal process. “We spent hundreds of hours improvising,” he says. “I would ask the cast to do anything different to what they were saying to open up the realm of movement, the subconscious.” So a young man describes being beaten up by his father, but the actor is incongruously buoyant, skipping with a rope through the scene.

Faith is still a subject that the British stage approaches gingerly. But for Newson, “the things that precipitated me wanting to do this were tied up with religion”. He first became aware that sexual politics might not sit happily with race and religion in the early 1990s. He and his then boyfriend, who was Indian, were barracked while walking hand-in-hand through London on a Pride march.

“That particular episode shook me up,” he admits. More recent controversies over homophobic Jamaican dancehall lyrics and the liberal West’s nervous response to Islamic fundamentalism have also informed the show, but anchored in individual experiences.

Newson chooses his words carefully, aware that he’s dealing with inflammatory stuff. But his essential conviction is inevitably contentious. “You will find the most extreme homophobic position, currently, is coming from Islamic fundamentalists – I want to stress, not from all Muslim people – and it needs to be discussed.”

Mainstream British culture, he believes, is too chary about tackling prejudice among religious minorities, as if it doesn’t have a right to take a position: “ We often say it’s their community.” Colonial guilt, he says, is inhibiting and has led to a strange “hierarchy of hate”.

“Why is homophobe not as potent a label as racist or Islamophobe?,” he asks.

Newson, who turned 50 last year, has frequently occupied controversial territory since he co-founded DV8 in 1986. Everyone from Tory MPs to gay activists have laid into shows about cottaging, body image or the serial killer Dennis Nielsen. If there’s a common thread, it's Newson’s unwavering sense of obsession (he’s turned down invitations to work with Madonna and Take That because he couldn’t feel the passion).

“When I’m making a piece I’m in a tunnel,” he says. “It’s hard for my friends, because for two years that’s all I talk about.” He admits that his chums may be relieved to see the back of To Be Straight With You and its dark, angry material.

To Be Straight with You opens at the National Theatre, London SE1, on Oct 29 and runs to Nov 15

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