I thought, 'It's Dick Cheney in a push-up bra!''

She's a two-time Oscar nominee, for The Help and Zero Dark Thirty, a woman respected for her thought-provoking performances, and someone who isn't afraid to speak up, whether that's against the industry's sexism, racism or indeed, ageism.

But even she feels helpless in knowing what to do, or where to begin, when you have the likes of Russell Crowe stating that older actresses who complain there aren't enough roles are simply looking in the wrong age bracket.

"I would love to see Sissy Spacek in the lead of a film again. She's a brilliant actress," remarks the star who refuses to disclose her age but is reported to be 37.

"And Kathy Bates, Geena Davis, Susan Sarandon, Jessica Lange - it goes on and on; incredible actresses who I really miss seeing in movies. These are women who aren't trying to play the ingenue, they're very comfortable in their skin. I can't wait to be working in an industry that has more roles available to them."

She believes there needs to be more women behind the camera, and directing and writing - something she hasn't ruled out for herself in the future.

"I'm very happy being an actress, but of course, if there's something I can do to help [improve the situation], then I absolutely would," continues the red-haired Chastain, looking flawless (despite being "super-jet-lagged") in a high-neck black dress.

Last year's sci-fi blockbuster Interstellar was an eye-opener, she reveals. Her character Murph was originally meant to be a man, but director Christopher Nolan decided to change it. "What's amazing is he didn't change much about the character," she's since remarked. "It inspires me to look at scripts that were written for men and see how easy it would be to change the part to a female."

In her new movie, the thriller A Most Violent Year, she plays Anna Morales, the steely wife of Abel, played by Oscar Isaac, an immigrant and heating oil businessman, operating in the crime-ridden New York of 1981, statistically one of the most dangerous times in the city's history. They're the living embodiment of the nouveau riche, and the film explores their determination to climb up a morally crooked ladder.

Of course, this isn't simply a 'wife of...' role for Chastain.

"When I read the script, I thought, 'It's Dick Cheney in a push-up bra!'" she says, laughing.

"You have this idea of her from the beginning, and then by the end, you realise she's running the whole company."

Often gracing magazine covers and one to watch on the red carpet, it's no wonder Chastain, whose breakout role was in 2011's mind-bending The Tree Of Life opposite Brad Pitt, enjoyed the transformation into the uber-wealthy and immaculate Anna.

"It's such a big deal, the costume, hair and make-up, it's everything for me when I'm playing a character," says the California-born actress.

"It was really important she have blonde hair, but not the Eighties stereotype where it's teased and frosted. I wanted her to show money - the best hairdo, the best nails, the best clothes." It's why she got in touch with her good friend Roberta Armani, niece of Giorgio Armani, during pre-production.

"Mr Armani was all about that time and the power suit," says Chastain, who's dating fashion executive Gian Luca Passi de Preposulo.

Her co-star, channelling a young Al Pacino, doesn't look too bad either. She and Isaac go way back, to the days when they were studying at New York's prestigious performing arts school, Juilliard.

"We've been friends for over 13 years. We've always really supported each other, gone to each other's premieres, kept in touch and worked hard to try and find a project to do together," says Chastain, who introduced A Most Violent Year's director J.C. Chandor to Isaac shortly before his career breakthrough with the Coen brothers' Inside Llewyn Davis.

"Of course, there was the fear of, 'We've been dreaming of doing this for years and years, I hope it's OK', but it's one of the best experiences I've ever had on set."

For that reason, and the positive feedback the film's receiving, she insists she wasn't disappointed by being snubbed when this year's Oscar nominations were announced.

"Not at all, not at all," Chastain says calmly. "This is one of the best reviewed films in the United States and it's doing really well here. Interstellar got nominated for five Oscars; I got nominated for a Golden Globe and won a Critics Choice, so I have a lot to be really thankful for."

EXTRA TIME - BEHIND THE SCENES

:: J.C. Chandor originally set the film during the summer months, but was forced to rethink when scheduling issues forced the 40-day shoot to move. It turned out to be one of the harshest winters in New York's history.

:: One of Oscar Isaac's suits was a replica of a garment costume designer Kasia Walicka-Maimone spotted in a Barneys ad from the era. It was recreated by a Brooklyn-based company whose clientele includes President Obama.

:: Jessica Chastain met with a vocal coach, a Brooklyn local, who helped her hone Anna's thick New York drawl.

:: Look out for Brit actor David Oyelowo, who plays Abel's adversary and is also starring in the upcoming Martin Luther King Jr. biopic, Selma.

:: Director of photography Bradford Young was keen to avoid conventional images of NYC, as seen in the likes of Taxi Driver, and highlight the decay of that period instead. No easy task, given it's a city "that's almost 180-degrees different" to what it was during the early Eighties, he says.

:: A Most Violent Year is out in cinemas now