London, UK - Friends co-creator Marta Kauffman has said it was a "mistake" not to use appropriate pronouns in the hit sitcom and now ensures she builds "safe" and "tolerant" workplaces.

During an interview with The Conversation on the BBC World Service, Kauffman (65), who co-created the show with David Crane, has spoken about her regret at the representation of Chandler Bing's transgender parent.

Kauffman said: "We kept referring to her [Chandler's transgender parent] as Chandler's father, even though Chandler's father was trans."

"Pronouns were not yet something that I understood. So we didn't refer to that character as she. That was a mistake."

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Kauffman, who is also the creator of Netflix hit Grace And Frankie, said she now strives to create inclusive and diverse workplaces.

"I like very much to create an environment where we have a happy set and a happy crew," she said.

"It's very important to me that where we are is a safe place, a tolerant place, where there's no yelling."

"I fired a guy on the spot for making a joke about a trans cameraperson. That just can't happen."

On how she deals with criticism of the show, Kauffman told presenter Kim Chakanetsa: "Friends has been criticized in a number of ways. The biggest one being that we did not have enough representation of Black people."

"And over the course of the last few years I've gotten to the point where I can say unfortunately yes, I am guilty of that. And I'll never make that mistake again."

"I was clearly part of systemic racism in our business. I was unaware of that, which makes me feel stupid. That was a very valid, extremely difficult criticism which still... I get emotional about."

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She added: "If I knew then what I know now, there are certain things I would have changed. But I didn't know them and I have since learned."

Kauffman also recently announced that she will pledge $4 million to her alma mater, Brandeis University, to establish an African and African American Studies professorship.