The polarising star, 55, cut off Susanna Reid, 49, as she attempted to read a statement from the government.
Many viewers accused Piers of being bullying as he spoke over his co-host.
And former Strictly Come Dancing judge Arlene Phillips has now waded into the incident.
The choreographer, 77, publicly denounced Piers' behaviour via Twitter.
She tweeted: "Whoa @piersmorgan on @GMB today. Yes, you are right to challenge the government the way you have and I support that but please do not ever shout down your brilliant other half @susannareid100."
However, Piers didn't respond well to her words. Instead of apologising he adamantly defended his actions.
He replied: "We were told to read out a Govt statement. But why should we when the Govt is boycotting us? I was registering my protest."
Many of Arlene's fans agreed with her stance on the social media platform.
One user responded to her choice words with: "Was awful and uncomfortable to watch him talk over her the way he did."
A second user agreed with: "Dreadful behaviour. So disrespectful to @susannareid100."
And a third user tweeted: "Thank you @arlenephillips. He was totally out of control so rude! And yes @piersmorgan I did want to hear the statement."
A fourth viewer commented: "It was disgusting how he spoke to @susannareid100.
"He must apologise on air for his behaviour. He needs to remember it’s not his show, he gets paid to give out the news.
"It was disgusting"
"He works with a team and should respect them."
The debacle occurred when Susanna attempted to read a government statement in response to Piers' criticism of its handling of student nurses.
However, Susanna barely got a word in as Piers continually spoke over her.
Furious that Government ministers had refused to appear on the show for weeks now, he lashed out.
He asked: "Sorry, why have we got to read this?"
"If a government won’t come on our programme, why should we read their wishy-washy statement? If they want to have their statement read then come on the programme."
Susanna repeatedly asked if she could read the piece.
She asked: "Well, can I read the statement?"
But Piers refused, and even covered his ears in defiance.
What do you think of Arlene's words? Share your thoughts with us on our Facebook page @EntertainmentDailyFix.