In her latest film she plays an alcoholic divorcee who is battling the heartbreak of failed fertility treatment.

And now Emily Blunt has waded into the somewhat sensitive debate about motherhood - saying women can descend into cruelty towards each other when they become involved in the "mummy cult".

The 33-year-old made the controversial comments last night at the London premiere of her new film, The Girl On The Train.

The film - based on Paula Hawkins' bestselling novel - sees her play Rachel Watson, who becomes infatuated by the seemingly-perfect couple she sees through the window during her daily train journey.

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Mother-of-two Miss Blunt said: "In the domestic world, I think it's when women can be a bit cruel about each other, more so than any other environment.

"I think there is a huge societal pressure on women when it comes to motherhood, this sort of mummy cult that goes on.

"It sort of makes women feel that they have to be a bit defensive about the choices that they make, whether they want to be a mother, whether they don't, whether they want to breastfeed, whether they don't.

"And I think this film really captures that."

In the film, Rachel is in mourning for the pregnancy that never happened, while Megan Hipwell - one half of the "perfect" couple - does not want a baby at all.

Blunt, who wowed in an embellished floral gown was joined on the red carpet by Miss Hawkins.

The actress said she was braced for "some resistance" to her version of Rachel by fans of the book.

"I think any time a character or certainly a book is beloved, you're going to be met with some resistance to whoever is cast or whoever is doing it," she said.

Responding to critics who said she was too pretty to play the troubled character, she said: "I think people should see the film before they decide if they think I look pretty or not."