The Oscar-winning actress was appearing on the programme to promote her new film Arthur, in which she appears alongside Russell Brand.
Discussing the work she did with John Gielgud, who died in 2000, Mirren admitted that her fellow actor had sworn a lot.
"Well in that sort of wonderful voice he had," she told Bill Turnbull and Sian Williams, before impersonating him by saying: "You little s**t."
However, she quickly realised her mistake and exclaimed, "I'm so sorry! I do apologise."
The presenting duo also apologised to viewers, saying: "If you heard that, we're very sorry."
The 65-year-old star previously told the BBC that she believes that "the whole drama of swearing is so overblown", adding: "It's idiotic that it's made into such a big deal."
A BBC spokesperson added: "Bill Turnbull apologised straight away and we're sorry if anyone was offended."
> Helen Mirren 'was scared of Russell Brand'