After announcing his final North American tour, Sharon Osbourne is accusing AEG of using block-booking practices to force Ozzy into performing at the Staples Center in Los Angeles, Billboard is reporting.

Read more: Ozzy Osbourne announces final North American tour

According to the music news source, Sharon accused the events company of “a staggering attempt to blackmail” Ozzy into playig the Staples Center in Los Angeles, which was reportedly presented as a deal for a concert at the London's O2 Arena.

Basically, for Ozzy to play at the O2—owned by AEG—he would have to play the Staples Center as well, which AEG owns.

“Shame on AEG for bringing artists into a power struggle you're having with your competitor, Live Nation,” Sharon Osbourne wrote to AEG Live chairman/CEO Jay Marciano. “I can assure you that Live Nation would never strong-arm an artist into playing a venue they're not comfortable performing in.”

Marciano responded, saying: “Thank you for your note. Please understand this dispute is between The Forum and Staples Center and we couldn't agree with you more — it should always be the artist's choice. We long for the days when artists and fans came first.” 

However, her response points to the fact that in order to remain a free market, then things need to change.

“This is a staggering attempt to blackmail OZZY into playing your venue in Los Angeles,” she wrote, the music source reports. “It is also a complete abuse of bargaining power and not conducive to a free market. If you do not confirm the date for OZZY at the O2 in London then I will be forced to take legal action against AEG Live! without delay.”

As Billboard explains, this isn't the first time there has been issues with block booking at the Staples Center and London O2. However, this is the first time a major artist has openly spoken up—and threatened legal action.