Amanda Holden apologised after shouting a swearword while taking part in a ghost act during the first Britain’s Got Talent live semi-final on ITV.
The judge was visibly scared when she was put through a spooky routine by an act called The Haunting on Monday.
She shouted the profanity near the end before clasping a hand over her mouth.
After returning to the judges’ desk, she said: “I just really want to apologise if I said anything. I said a really terrible word.”
The segment was shown just after 20:00 BST. Holden added: “I know there are kids watching, I know my kids are watching, so massive apologies. I can honestly say I feel terrified.”
Around 5.5 million people were watching at the moment of her exclamation, according to overnight viewing figures.
Afterwards, presenter Ant McPartlin added: “We’d like to apologise if you heard any bad language there from Amanda. She was very, very scared as you could see.”
The segment involved Holden being led to a room beneath the stage and confronted by actresses playing the “ghosts” of a woman called Agatha and her 11-year-old daughter Florence.
In a video posted on Twitter, Holden said: “I’ve never felt so terrified in my whole life. I wouldn’t want anyone to go through that, but she’s a genius. I don’t know how she does it. And apologies again.”
The moment has been cut out of the show on ITV Hub but was shared by several viewers on social media.
On ITV2’s Britain’s Got More Talent, Holden said she had asked head judge Simon Cowell not to fire her from the show for swearing.
In response to a question from a caller about what the judges do during the ad breaks, she replied: “I had a panic attack and went to the toilet. Lots of times.”
The Haunting was voted in the night’s top three acts by viewers, but was not among the two who went straight through to this weekend’s final.
PC Dave Wardell and his retired police dog Finn automatically qualified after topping the vote, and the judges chose Flakefleet Primary School over The Haunting to take the second spot.
However, The Haunting still has a chance of making it to the final as the judges’ wildcard. Four more semi-finals will take place this week before the final on Sunday.
Monday’s show began with Ant and Dec performing an elaborate song and dance act that culminated with them revealing that judge Alesha Dixon is pregnant.