The presenter was heard complaining about a malfunctioning ear piece when he should have been reading out the headlines on the ITV breakfast show.
As images from the apparent terrorist attack at Finsbury Park were shown on screen, Piers was heard ranting at bosses in the gallery.
Clearly unaware that his microphone was live, Piers fumed: “I still can’t hear anyone in my bloody ear.
“I don’t know what is going on with this. This has been going on for a week now. Could someone talk to me? I’m not hearing anyone!”
Someone was eventually heard telling Piers he was on air, and he subsequently toned things down and began reading the headlines.
Piers recently confessed how ‘Good Morning Britain’ is “slowly killing him” and has turned him into a “complete zombie” due to the early starts.
Speaking to The Mirror, Piers said: “It’s killing me before my very eyes. It’s the least healthy existence imaginable.
‘Good Morning Britain’ airs weekdays from 6am on ITV.