Days after Jennifer Lawrence penned an essay bemoaning the gender pay gap, her frequent collaborator Bradley Cooper urged his fellow actors to be "more transparent" about their salaries, so their female co-stars could be clear about they're worth to the movie studios.

Now a new Care2 petition has been launched to encourage Clooney to follow Cooper's lead and reveal his salary information.

Almost 10,000 people have already signed the petition, which was written by feminist Julie Rodriguez.

"While it's easy to dismiss the concerns of professionals like Jennifer Lawrence as coming from a place of privilege most of us will never know, the fact is that sexism in Hollywood reflects sexism within our culture in general," she says. "Whether a woman is being paid millions less than her co-workers or just losing a few extra dollars an hour, pay inequality is unacceptable in 2015."

She adds, "George Clooney has taken a stand on civil rights issues across the world. I hope he'll consider pledging to fight the pay gap in his own industry as well."

Last year (14), leaked emails from the Sony database revealed Lawrence and Amy Adams made less money from their Oscar nominated movie American Hustle than the film's male actors, Cooper and Christian Bale.

Lawrence felt compelled to address this in her essay, titled Why Do I Make Less Than My Male Co-Stars? for the 13 October (15) publication of Lena Dunham's Lenny newsletter.

"I would be lying if I didn't say there was an element of wanting to be liked that influenced my decision to close the deal without a real fight," she wrote. "I didn't want to seem 'difficult' or 'spoiled'.

"At the time, that seemed like a fine idea, until I saw the payroll on the Internet and realized every man I was working with definitely didn't worry about being 'difficult' or 'spoiled'."

Cooper was asked about the actress' essay in the days that followed, and told Reuters, "Usually you don't talk about the financial stuff, you have people. But, you know what, It's time to start doing that."

He was applauded for taking on the issue by his American Sniper co-star Sienna Miller, who revealed she pulled out of a Broadway play after learning her salary was a lot less than her male counterpart. She never named the production or her co-star.