Anti-harassment and bullying campaign group UK Time's Up proposed the idea.
Knightley said: "For anyone to fulfil their creative potential there cannot be fear or disrespect of any kind."
Harris added that "no-one should go to work fearful of harassment, bullying and abuse".
UK Time's Up is working with Creative UK, which promotes the development of creative companies, to agree a plan of action. They are also speaking with representatives from the music, TV, film, theatre, advertising, video games, and fashion sectors.