Women's rights activists are calling on bosses at sports giant Reebok to drop Rick Ross as a spokesman after he appeared to rap about using a date rape drug in new song U.O.E.N.O. (You Ain't Even Know It).

The hip-hop star is under fire for a controversial line he spits on rapper Rocko's new single, in which he says, "Put molly (slang for pure ecstasy) all in her champagne/ She ain't even know it/ I took her home and I enjoyed that/ She ain't even know it."

The offensive rhyme has already prompted protesters to sign a petition on Change.org in a bid to force Ross to issue a public apology for seemingly glorifying violence against women, but he spoke out against the criticism on Thursday (28Mar13) and insisted the uproar was all over "a misunderstanding" because he would never condone rape.

However, Ross failed to apologise for causing a stir and campaigners are refusing to let him off the hook for his boastful lyrics - members of anti-sexism group UltraViolet are now urging Reebok executives to take a stand and cancel his contract as a celebrity representative.

Nita Chaudhary, co-founder of UltraViolet, says, "We are appalled that Reebok would pay a spokesperson who brags about enjoying drugging and raping a woman.

"Reebok devotes a lot of time, energy and money to marketing to women - and now they are paying a man who is literally bragging about raping us while absurdly insisting it can’t possibly be rape if he doesn’t use the word 'rape'. Reebok is apparently Ok promoting rape culture, but when one out of five women are the victim of an attempted or completed rape, that has consequences."

The petition has already garnered more than 51,000 signatures within hours of launching online and UltraViolet demonstrators are planning to stage a protest outside Reebok's headquarters in Boston, Massachusetts next week (begs01Apr13) if company heads fail to respond to their campaign.