Image copyright Keith Bernstein Image caption Dame Helen Mirren's character pushes for the mission to change from 'capture' to 'kill' operation

Dame Helen Mirren has said actresses should go after roles written for men.

In her new film thriller Eye in the Sky she plays an army colonel, a role originally written for a man.

The actress said it made her "cross" that many roles were given to men regardless of whether it was the lead character.

"You look at a scene and it's going to be all men around a table and you think at least half of those could have been women," she said.

"It's so hard to get a job as an actress, let alone as a star but just a job - to be a working actress it's so much more difficult than it is for men".

Sandra Bullock last year revealed she had got her agent to find scripts with interesting male roles and then pursued them for herself. One of those roles was political drama Our Brand is Crisis, released in January, in which she played a campaign manager.

Dame Helen said the lack of roles for women was also markedly noticeable in the film industry when it comes to extras.

"The only time that there is more women on the set as extras is a swimming pool scene and they're all in bikinis - any swimming pool scene and suddenly it's full of women."

Image copyright Keith Bernstein Image caption Dame Helen's performance has been described as a "masterful portrayal" by the Washington Post and "one of her fiercest screen performances" by the New York Times

In Eye in the Sky Mirren plays an army intelligence Colonel remotely commanding a top secret drone operation from London, attempting to capture a group of terrorists from their safe-house in Nairobi, Kenya.

Although the role was originally written for a man the film's producers, who include actor Colin Firth and director Gavin Hood, had changed the part to a woman before it was offered to Dame Helen.

Something she thinks was an "astute decision" because it opened up debate.

"The film is about the discussions people have when they leave the cinema and having a woman in that role allows you to make that discussion," she said.

"As opposed to saying 'well that's men, that's what men do in war' ... I think Gavin very astutely understood and realised putting a woman [in the role] just changed the discussion."

Real time mission

The film follows the decision making process almost in real time as the mission turns from a "capture" to a "kill" operation as Colonel Powell realises that the terrorists are about to embark on a suicide bombing mission.

The debate becomes more complicated when a nine-year-old girl selling bread enters the kill zone.

Image copyright Keith Bernstein Image caption Alan Rickman's character has to deal with politicians and the attorney general as they try to decide on the legalities and moral choices in the mission

Also involved in the decision making is British Lieutenant-General Frank Benson played by Alan Rickman in his last on-screen role.

Dame Helen and Rickman did not act in any scenes together, but she said they had spoken about why they wanted to appear in the film.

"For him like me he wasn't doing it to play this wonderful role that 'ooh I might win an award with that role' - they're not those sorts of roles at all - both of us wanted to do it because of the nature of the film," she said.

The actress said she thinks the movie is a fitting tribute to him.

"I don't want it to be his last film, he left us much, much too early. It would've been wonderful to see his next 20 years of performances but I think it's a great way to say goodbye to him.

"Because I think it's a film that would appeal to his intelligence, his humanity - I'm sure why he did it in the first place."

Eye in the Sky is released on 15 April in the UK.