Three hundred female Hollywood actors, directors, writers, producers, agents and executives have launched an initiative called Time’s Up to help fight sexual harassment in the workplace.

Its supporters include Reese Witherspoon, Shonda Rhimes, Emma Stone, Cate Blanchett, Eva Longoria, America Ferrera, Rashida Jones, Kerry Washington, Ashley Judd, Natalie Portman, Meryl Streep, Steven Spielberg and Jennifer Aniston among others.

The project includes a projected $15m legal defence fund and was initially announced in a full-page advert in The New York Times, taking the form of an open letter.

Time’s Up is being described as a “unified call for change from women in entertainment for women everywhere.” The open letter which constituted the ad reads: “The struggle for women to break in, to rise up the ranks and to simply be heard and acknowledged in male-dominated workplaces must end; time’s up on this impenetrable monopoly.” It also calls for “gender inequality and the imbalance of power” to be addressed, stressing the need for more women to gain positions of authority and equal pay.

The defense fund, which is for both female and male victims of sexual harassment at work, is backed by donations and more than $13.7m has already been raised of its $15m target (at the time of writing). It is aimed primarily at those who cannot afford the payments to defend themselves.

Time’s Up will also include a push for legislation to penalise companies where persistent harassment takes place, as well as discouraging non-disclosure agreements that can silence victims.

The initiative comes in the wake of last year’s sexual abuse allegations against film producer Harvey Weinstein and other members of entertainment industry, and is a follow-up to the #MeToo Twitter trend, which saw women and men all over the world share their stories of sexual abuse and harassment.