Comedian and talk-show host Bill Maher came under sharp criticism on Saturday, after he used a racial slur while interviewing a U.S. senator on his “Real Time” show on Time Warner Inc.’s US:TWX HBO

Maher was interviewing Republican Senator Ben Sasse of Nebraska who was promoting his book, “The Vanishing American Adult.” Sasse invited Maher to visit Nebraska during banter between the two, adding “we’d love to have you work in the fields with us.”

Maher then used the epithet while making a distinction between slaves who worked outdoors and those that worked indoors, making a reference to himself. He immediately added that it was a joke.

But the comment caused an immediate backlash, lighting up Twitter and other social media with many calling for his firing or the cancellation of his show.

HBO was not immediately available for comment, although media reports said the network strongly condemned Maher’s use of the word.

“Bill Maher’s comment last night was completely inexcusable and tasteless,” HBO said in a statement to the Hollywood Reporter “We are removing his deeply offensive comment from any subsequent airings of the show.”

Maher later issued an apology.

“Friday nights are always my worst night of sleep because I’m up reflecting on the things I should or shouldn’t have said on my live show,” he said in a statement to Variety. “Last night was a particularly long night as I regret the word I used in the banter of a live moment. The word was offensive and I regret saying it and am very sorry.”

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Sasse also addressed the issue on his personal Twitter account on Saturday.