Labour delegates today unanimously backed a call for James Murdoch to quit as chairman of BSkyB.
Activists at the party's conference in Liverpool supported a motion demanding Mr Murdoch resign over the phone-hacking scandal at the News of the World.
Mr Murdoch also chairs the now-defunct tabloid's parent company, News International.
Unite general secretary Len McCluskey, who put forward the motion, said: "We're delighted today's motion is now Labour policy.
"Our party can say with pride that it will no longer tolerate the corruption of decent values sadly witnessed in some quarters of our media in recent times."
Urging delegates to back the motion yesterday, MP Tom Watson, who has led the campaign over phone hacking in Parliament, said: "Let's tell Ofcom what we think about James Murdoch. I wouldn't put him on the board of an ornamental garden.
"He's certainly not a fit and proper person to chair a major broadcaster."
Today's vote was passed with a unanimous show of hands.