Referring to Peta as "that idiot", it was clear there was no love lost between the TV host and the fiery performer.
"This is a woman ... who behind the scenes was ... rude to staff, rude to crew, didn't listen to anything [mentor] Darren [Hayes] and Delta had to say," Darren said.
"She was a primadonna, she knew better than everyone, she wasn't happy with the way the song was arranged, this that and the other."
Peta appeared on the show looking for a second chance after losing a record deal at the age of fifteen.
Delta was the only judge who turned around during Peta's jazzy version of Oasis' 'Wonderwall' which gained her access to the battle rounds and a place on Delta’s team.
Alas, her battle round performance of 'Purple Rain' turned out to be her swansong as she was voted out of the show in favour of opponent Viktoria Bolonina.
"[Peta] came out and absolutely killed one of my favourite Prince songs of all time," Darren said.
"It was hard to listen to when she was singing and screeching down the mike."
The Mornings hosts appeared startled by Darren's outburst, but he didn't hold back.
"This industry is about attitude right?" he said.
"That’s a perfect example of why you don’t deserve to be on the show and why you’ll never make it, because your attitude stinks."
Watch Peta's final Voice performance below: