Alyssa Milano has launched a social media campaign to encourage women to speak up about sexual harassment

She wrote on the micro-blogging website: "If you've been sexually harassed or assaulted write 'me too' as a reply to this tweet."

Alyssa revealed she'd borrowed the idea behind the powerful campaign from a friend.

Under her own post, there was a screenshot that read: "Me too.

"Suggested by a friend: "If all the women who have been sexually harrassed or assaulted wrote 'Me too.' as a status, we might give people a sense of the magnitude of the problem." (sic)"

And within a matter of hours, Alyssa's tweet had gone viral, with women all around the world responding to her request, including the likes of Evan Rachel Wood, Gabrielle Union and Lady Gaga.

Gabrielle wrote, simply: "This. #MeToo (sic)"

Evan, 30 - who revealed she'd been raped "many years ago" during an interview conducted in 2016 - explained how her own experience caused her to "shut down".

The actress tweeted: "Being raped once made it easier to be raped again. I instinctually shut down. My body remembered, so it protected me. I disappeared. #metoo (sic)"

Meanwhile, Gaga - who previously revealed she was raped at the age of

19 - also lent her support to the campaign.

She tweeted: "#MeToo (sic)"

Alyssa's decision to launch the campaign came shortly after she spoke out against Hollywood movie producer Harvey Weinstein, who has been accused of sexually harassing women for decades.

The actress recently said: "While I am sickened and angered over the disturbing accusations of Weinstein's sexual predation and abuse of power, I'm happy - ecstatic even - that it has opened up a dialogue around the continued sexual harassment, objectification and degradation of women."