'All-time low': Piers Morgan slammed for impersonating Greta Thunberg

Piers Morgan isn't known for holding back on mocking those he disagrees with, but some say his latest tirade went too far.

In an impassioned rant live on air, the Good Morning Britain host criticised climate change protest group Extinction Rebellion for disrupting cities around the world with protests.

He was particularly incensed by a photo of protesters stopping at a McDonalds for lunch, calling them "shameless hypocrites". 

"We all want to save the planet, but I'm not lying on the floor screaming, going to McDonald's, generally behaving like imbeciles."

Morgan then shifted his target to Greta Thunberg, the 16-year-old Swedish activist whose fiery speech at last month's UN summit ignited a worldwide debate over whether today's youth have been let down by political inaction on environmental destruction. 

"How dare you, how dare you?" Morgan said in a mock-Swedish accent. "You have stolen my morning, you have stolen my airtime. I have no life. How dare you?"

Co-host Susanna Reid was vocal about her disagreement with Morgan's comments, and she wasn't the only one. Viewers took to Twitter to voice their displeasure.

"Now you have stooped to an all-time low, mocking a child with Aspergers?!" one user said. "Piers v Greta? I know who I would put my money on…"

"How dare Piers Morgan mock Greta Thunberg, why do GMB give him the time of day and pay him for his disgusting comments?" another said. 

"Putting on an accent and mimicking a 16-year-old girl is bullying," one woman wrote. "You should be ashamed!"

"What is it about Greta Thunberg that makes grown men totally lose any sense of decorum or dignity?" one said. 

"Piers Morgan’s outburst against Greta [and] the young climate change activists is indicative of his frustration with life," another said, going on to suggest the 54-year-old belonged in a zoo with "dinosaurs". 

It's not the first time Morgan has criticised the teenage activist - he recently expressed scepticism about the possibility of her being awarded the Nobel Peace Prize. 

"What’s she done for peace, exactly?" he tweeted. "She’s got just very very angry about climate change, abused loads of adults and terrified millions of children."