Howard Stern has slammed Simon Cowell over Gabrielle Union's departure from 'America's Got Talent'

During his SiriusXM show, Howard - who was a judge on the show for four seasons until 2015 - said: "He sets it up that the men stay no matter how ugly [the men] are, no matter how old they are, no matter how fat they are, no matter how talentless they are. He replaces the hot chicks with hotter chicks and younger chicks. Howie's [Mandel] doing a fine, serviceable job - why don't they change him? And why don't they change Simon? This is the ultimate example of a boys' club."

Gabrielle, 47, reportedly had concerns over racially insensitive acts and personal remarks about her appearance before she left the show but Julianne, 31, has denied experiencing any problems on set.

She said in a statement last week: "I had a wonderful time on 'America's Got Talent.' I loved working with the cast, crew and producers. I am happy to continue my working relationship with NBC... I'm looking forward to what the future holds."

However, NBC says it is taking Gabrielle's concerns seriously, explaining: "We remain committed to ensuring a respectful workplace for all employees and take very seriously any questions about workplace culture.

"We are working with Ms. Union through her representatives to hear more about her concerns, following which we will take whatever next steps may be appropriate."

Time's Up has launched a petition urging NBCUniversal leaders to take Union's allegations seriously and to take steps on workplace health and safety.

Time's Up president and CEO Tina Tchen said in a statement: "Gabrielle Union's experience at 'America's Got Talent' is exemplary of the double bind that black women face at work.

"Not only did Union reportedly endure and witness racist and inappropriate behaviour - including racially-insensitive comments and excessive criticism about her physical appearance - but it also appears she was punished for speaking out: the company labeled her as 'difficult' before ousting her from the show altogether. Union's story is deeply troubling on its own, but her experience is particularly problematic because it follows a pattern of NBCUniversal protecting the careers of powerful men at the expense of women who speak out."

SAG-AFTRA added: "We take issues of workplace health and safety very seriously. We immediately reached out to Ms. Union's representatives when these reports came to light. It is our practice to work closely with members who reach out to us and their representatives in instances like this, as that usually affords the best protection and best resolution for the affected member."