Glee star Heather Morris has admitted that Lea Michele was "unpleasant to work with" amid revelations about the actress's bad behaviour while working on the show.

Michele yesterday apologised for "immaturity" and how her co-stars had "perceived" her behaviour during the six seasons of the show after actress Samantha Marie Ware alleged that she had made her first TV gig "a living hell".

Drag Race star Willam then accused Michele of "subhuman" treatment, claiming that he pulled out of an appearance on the show due to her, while an extra said that he had been told by Michele that he "didn't belong" on the same lunch table as the main actors.

Morris, who played the deadpan Brittany S. Pierce on the show, said that Michele deserved to be "called out" for her behaviour behind the scenes but warned against jumping to the conclusion that she is racist.

"Let me be very clear, hate is a disease in America that we are trying to cure, so I would never wish for hate to be spread to anyone else," Morris wrote in a lengthy post on Twitter.

"With that said, was she unpleasant to work with? Very much so; for Lea to treat others with the disrespect that she did for as long as she did, I believe she should be called out. And yes, it's also on us because to allow it to go on for so long without speaking out is something else we're learning along with the rest of society.

"But, at the current moment it's implied that she is a racist and although I cannot comment on her beliefs, I think we're assuming, and you know what happened when we all assume."

Michele has yet to make further comment since posting her statement via Instagram on Wednesday.