Director Mira Nair on The Reluctant Fundmentalist

She was keen to watch rising star Riz Ahmed – who played a would-be terrorist – at work. She also wanted to see how Chris Morris would handle the story of a group of anti-Western British Muslims.

“It’s so filthy!” says Nair, 55. “The obscenities! We took the whole family and to hear that strong peasant language ... I had a fab time!”

It was when trying to secure funding for her own take on East-West relations that the fun stopped. “It was an ugly, lonely struggle — a sacrifice on so many levels. I thought, ‘Oh f***, maybe the universe is conspiring for this not to happen.’”

Nair, as you can see, is pretty filthy, too, the colourfulness of her language just one of the things that makes her stand out on the junket circuit. As for her thriller, no wonder the backers were scared.

Based on the novel by Mohsin Hamid, The Reluctant Fundamentalist is set in New York, Lahore and Istanbul and co-stars Kiefer Sutherland, Kate Hudson and Liev Schreiber. Its hero is Changez (Urdu for Genghis) Khan — played by Ahmed — a young Pakistani who smiles as he watches the Twin Towers collapse on 9/11.

Changez becomes disgusted not only by his job as a financial analyst in Manhattan but by the middle-class mores of his white American girlfriend, Erica (played by Kate Hudson), and returns to Lahore as a professor. He recklessly tells a CIA-connected journalist: “I had seen the arrogant America – the blindness, the hypocrisy, the xenophobia ...”

Nair’s films have always been socially aware (as those familiar with her early effervescent hits, Salaam Bombay! and Monsoon Wedding, will testify). Nor is she a stranger to controversy. Her 1996 epic Kama Sutra: A Tale of Love was banned in India, while in 2008, a short called How Can It Be? was seen by some as an insult to Islam. Still, The Reluctant Fundamentalist is definitely the biggest, and most potentially explosive, project to date.

Perhaps unwisely, Nair is willing to discuss the 9/11 attacks, which she describes as “audacious” because they were about faith and conviction rather than money. She then describes Changez’s revelation about what a Wall Street “economic training” entails. “He sees through it,” says Nair. “You know, that moment when you ask yourself what you’re doing? And [you realise]: You’re serving the Man. Serving the Man who is dropping bombs on your people.” Then she stops. “Perhaps you shouldn’t quote that.”

I mention that the themes of the film tie in closely with the work of her professor husband, Mahmood Mamdani (a Ugandan who teaches mainly in Kampala). In Good Muslim, Bad Muslim, he writes: “The CIA created the mujahideen and Bin Laden as alternatives to secular nationalism.”

Nair grips the arms of her chair, like an air passenger braced for turbulence. “I’m not sure I would put all the focus on the CIA. But American foreign policy – the execution of it – has definitely contributed to the problems. These people say, ‘We are here to save the situation.’ But who are they, to be the policeman of that gate?

“Look, while we were writing the script, history was in front of our eyes. [In January 2011] Raymond Davis, this American guy, listed as a financial officer at the embassy, is in his car, at a Lahore junction. He thinks these people on a motorbike are threatening him and he kills them in cold blood. And, of course, he was CIA. There was a huge furore because he was taken out [of Pakistan] and there was talk about blood money ... And look at the raid on Osama. The information, that came from somewhere ...”

Nair takes a deep breath. “But this is too hot for me to talk further on.” We move on to cultural politics.

In the movie, Erica creates an art installation that uses the words “throw on a burqa”. Nair says Erica is based on real Americans (Nair went to Harvard and for the past three decades has had a base in New York). “I’ve had so many friends like this. Erica’s repeating something Changez said, but it was a joke. He was teasing her. She takes him literally. Erica is hoping to create edgy art, which will break the ceiling of stereotypes. She’s a do-gooder. She’s like, ‘I’m coming to save you! I will help.’ But it’s unasked-for help. It’s so objectifying.”

Nair herself would never wear a burqa, or even a hijab (“I married into a Muslim family but my husband isn’t practising. I didn’t convert. As for the hijab, I’m just not that type of person, since it’s a conformist act. I like to not carry the badge of belonging to X or Y.”) But she believes women have the right to choose to wear such clothes.

There’s been much fretting in the Western press about “urban Talibanisation” (the trend for children of the rich to adopt strict Muslim dress codes). Nair pooh-poohs such fears. “My niece is a lovely fashionista. She’s taken the hijab but it’s not at all a curbing of her expression. The reverse. She works it into her ‘look’. I am a believer in adventure. You have to experience life, have this openness to it.”

Nair hates laying down the law, yet I’ve read that her son was “forbidden” to speak English in their various homes around the globe. “Mahmood was more strict than me on this issue,” says Nair, then surprises me by adding, “and thank goodness he was!” She’s proud that Zohran (now 21 and at college) speaks such fluent Hindustani. “Now, Zohran reprimands me when I speak English to him. He would prefer us to speak in our language, which is a lovely thing. In fact, when we go back to India, Zohran is the only one speaking Hindustani. His cousins in Delhi are all English, English, English. It’s terrible.”

Another glance at the tape recorder. “You are so mischievous, you are going to write that. Oh God!”

Nair’s loose tongue is a liability. It’s also (one could argue) her greatest asset. She’s a charmer with an urge to confound. You don’t know what she’s going to say next. And the same goes for her films.

The Reluctant Fundamentalist isn’t perfect, yet its best moments are electrifying: sublime, witty and generous.

At the end of the interview, Nair shakes my hand vigorously and says: “Come to Kampala!” She is, and isn’t, teasing. Were I to turn up on her doorstep, I bet we’d have a fab time.

• The Reluctant Fundamentalist is released on 10 May.