A host of stars including Westworld's Tessa Thompson and Oscar winner Brie Larson have lent their support to a new Time's Up initiative to boost the number of movies directed by women in Hollywood.

The #4percentchallenge is an online campaign aiming to increase the number of women directing major studio films. 

It calls on stars and studios to commit to announce a project with one female director on a feature film in the next 18 months. 

The hashtag refers to research shared by Time's Up movement that only 4% of the top grossing 1,200 films made in the past decade were directed by a female.

In a statement, the organisation said: "We are supporting women directors from all backgrounds in this challenge, as studies show that women-directed films are more inclusive in terms of girls and women on screen, female characters 40 years of age and older and underrepresented racial/ethnic groups.

"Women directors also hire other women in key behind-the-camera roles. The aim is to humanize production processes so that all groups can thrive at work in safe contexts."

A number of high-profile names have already pledged their support of the campaign.

As well as Tessa Thompson and Brie Larson, actress Susan Sarandon, comedian Amy Schumer, Outlander star Caitriona Balfe, Crazy Rich Asians star Constance Wu, Eva Longoria, Jennifer Lopez, Get Out director Jordan Peele, Big Little Lies actress and executive producer Reese Witherspoon, Bridesmaids director Paul Feig and Academy Award winner Natalie Portman are among those showing their support.

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