The programme, which aired on BBC Two on Saturday (1 August), covered the US confederacy and the history of slavery.
During a walkthrough of the time, Worsley talked about the reaction to president Abraham Lincoln’s speech in 1865, which declared that black people should have the right to vote.
John Wilkes Booth, the confederacy supporter who went on to assassinate Lincoln days later, was enraged by the declaration, she explained.
Speaking to the camera, Worsley told the audience: “He said, and his words carry a health warning, ‘That means n****r citizenship. By God, that’s the last speech he will ever make.’”
The episode, which was a repeat of a programme that first aired on BBC Four in 2019, received a backlash on social media as viewers questioned why the word had not been censored.
In response to one viewer who called out Worsley for saying the slur on national television, the presenter tweeted: “You’re right, it wasn’t acceptable and I apologise.”
A BBC spokesperson previously told The Independent: “This is a history programme about the American Civil War and features contributions from a number of African American scholars.
“Content information about the nature of the film was given before the programme started, and presenter Lucy Worsley gave a clear warning to the audience before quoting John Wilkes Booth as the term clearly has the potential to cause offence.”
The criticism comes after an earlier instance, in which the BBC aired a news report where a reporter used the “n-word” while describing a racist attack on an NHS worker.
Fiona Lamdin, social affairs correspondent, told viewers: “Just to warn you, you’re about to hear highly offensive language” before using the term.
After the clip aired, the BBC received a number of complaints and later pulled the report from its catch-up service.