Network sources have tried to hose down rumours of tension between Carrie, 37,and Lisa, 58, for months, but insiders say it's now at a flashpoint, with Carrie finding it increasingly difficult to "keep up appearances" and pretend they are friends.
"It's become a war between the Sunday Project and The Project," our insider claims. "Carrie cannot believe the money being thrown at Lisa's travel and overseas interviews, and she's furious that Lisa has the pick of any interviews – and takes all the big ones. You have to remember The Project is Carrie's show."
Their secret feud exploded a week ago when Lisa landed the plum interview with The Bachelor star Nick "Honey Badger" Cummins.
"It does feel a bit like Lisa rubs Carrie's nose in it when she posts shots of herself on location around the world, while Carrie is left holding the fort," our source says.
"Lisa was in London last week and the USA before that, and while Carrie is pregnant and can't fly, she was absolutely furious that Lisa was given the interview with the Honey Badger over her, as that was shot here in Australia."
Ever since it was reported that Lisa was given a $2.3 million salary – almost five times Carrie's $500,000 salary – the popular host has felt sidelined. To add insult to injury, Carrie has also had to try to hide any tension – and there's been plenty!
"She's poured her heart and soul into The Project – it's her baby. Now she feels like someone has swept in and stolen the limelight from under her," our source says.
"She's trying really hard to not let the bitterness show, but as Lisa gets given more exclusives, it's becoming harder for Carrie to keep up appearances.
"There's also a view among older staffers that Lisa's long interviews just don't work on The Project – and it seems the fans agree because the ratings have dropped since she joined."
WATCH: Reports of behind-the-scenes fighting between Carrie Bickmore and Lisa Wilkinson.
And it's not only Lisa who Carrie has in her sights, with the mum-of-two letting it be known on the show that she was anything but impressed with Kerri-Anne's passionate defence of shock jock Alan Jones on morning show Studio 10.
"I think I'm banned from appearing on The Project because I'm too right wing," laughed an unrepentant Kerri-Anne, 65, when asked about reports of tension among the top female stars at Ten, including claims she and Studio Ten host Sarah Harris, 37, were at loggerheads.
"I'm not out to steal anyone's job. I'm only doing two days a week, and I don't want to do more than that because I have a very full life outside of that. I am, however, going to do my very best to make waves. I'm not there to be a wallflower!"