Rocker Ozzy Osbourne is going off the rails against one of his Black Sabbath bandmates.

The "Godfather of Heavy Metal" claims guitarist Tony Iommi illegally claimed sole ownership of the band's name, in a filing with the US Patent and Trademark Office.

Osbourne is suing Iommi for a 50 percent interest in the "Black Sabbath" trademark, along with a portion of Iommi's profits from use of the name.

The Manhattan federal court suit also charges that Osbourne's "signature lead vocals" are largely responsible for the band's "extraordinary success," noting that its popularity plummeted during his absence from 1980 through 1996.

Courtesy: New York Post

Update:
Ozzy releases statement in regards to the lawsuit:

"It is with great regret that I had to resort to legal action against my long-term partner Tony Iommi, but after three years of trying to resolve this issue amicably, I feel I have no other recourse.

"As of the mid-1990s, after constant and numerous changes in band members, the brand of 'Black Sabbath' was literally in the toilet and Tony Iommi (touring under the name Black Sabbath) was reduced to performing in clubs. Since 1997, when Geezer [Butler, bass], Bill [Ward, drums] and myself rejoined the band, Black Sabbath has returned to its former glory as we headlined sold-out arenas and amphitheatres playing to upwards of 50,000 people at each show around the world. We worked collectively to restore credibility and bring dignity back to the name 'Black Sabbath,' which led to the band being inducted into the U.K. and U.S. Rock And Roll Hall of Fames in 2005 and 2006, respectively.

"Throughout the last 12 years, it was my management representatives who oversaw the marketing and quality control of the 'Black Sabbath' brand through Ozzfest, touring, merchandising and album reissues. The name 'Black Sabbath' now has a worldwide prestige and merchandising value that it would not have had by continuing on the road it was on prior to the 1997 reunion tour.

"Tony, I am so sorry it's had to get to this point by me having to take this action against you. I don't have the right to speak for Geezer and Bill, but I feel that morally and ethically the trademark should be owned by the four of us equally. I hope that by me taking this first step that it will ultimately end up that way. We've all worked too hard and long in our careers to allow you to sell merchandise that features all our faces, old Black Sabbath album covers and band logos, and then you tell us that you own the copyright.

"We're all in our 60s now. The Black Sabbath legacy should live on long after we have all gone.

"Please do the right thing."

Ozzy also expanded on the suit online in the following post:

"I am very saddened that I've had to take legal action against Tony. This is something that I've tried to avoid for years. I am not Geezer or Bill's voice. However, 'till the day I die I will not change my mind on this issue. The Black Sabbath trademark should be equally owned by Geezer, Bill, Tony and I as the true Black Sabbath lineup is Tony, Geezer, Bill and I. We've all been mates since school. I've always said there is an invisible thread that holds us together.

"Tony, let's get this ridiculous issue sorted and move on with our lives. You're 61, I'm 60. I hope that we've got a good 20 years left in us. But if not, God forbid something happens to you. What's going to happen to the Black Sabbath trademark? Who's going to oversee it? Don't you think after we're long gone the rights should stay in your family, my family, Bill's family and Geezer's family?"