It all unfolded as Piers, 53, hosted the programme alongside regular co-presenter Susanna Reid.
He told the camera: “I’m a Londoner, I’ve lived here for the last 30 years on and off, I want answers from my mayor.
“Why are you just lying in bed not answering them?
“Why do you indicate you’ll come on and then not come on, it’s gutless isn’t it? Anyway…”
Last night saw Piers take to Twitter to call out Sadiq for not making an appearance on the morning show.
He wrote: UPDATE: “London Mayor @SadiqKhan will not be appearing on @GMB tomorrow.
“He’s bottled it once again.
“Meanwhile, moped & knife crime continue to rocket on his watch.
“Your silence is shameful, Mr Khan.”
The demand for answers about moped crime by Piers comes after Amanda Holden posted a troubling video that reportedly showed two men in motorbike helmets dismounting mopeds and targeting a woman and child in broad daylight.
This isn’t the first time Piers has taken Sadiq to task as last month he also called for the Mayor to stand up and talk about knife crime in London on the show.
He said: “How do we end this violence? Well, the absence of the Mayor of London and the Home Secretary – both of whom we invited on this programme. And if Sadiq Khan is watching this, what are you hiding from?
“Why wouldn’t you come on a big morning TV programme to talk to our viewers – many of whom live in London, many of whom are worried about what’s going on.
“This is your duty, we’re not doing it as some sort of trap. You’re supposed to come on and defend yourself. But no, you just hide behind your social media account and not come on.”
Sadiq did appear on the programme several days later, however, Piers was not present.
Piers posted to Twitter to vent his frustration at Sadiq for not appearing when he was asking the questions.
He raged: “Great to see @SadiqKhan on @GMB today talking about the terrible threat of junk food on public transport.
“Especially as he refuses to come on @GMB when I am there to talk about the explosion in knife crime happening on his watch. Grow a pair, Mr Mayor.”
Good Morning Britain airs weekdays at 6am on ITV.