He's also said he never thought he'd be good enough to host the Today show for so long.
In a statement, Nine's director of news Darren Wick said the network and their Gold Logie victor had agreed it was "time for him to step off the Today show".
'Karl remains on contract with the network and will continue to host This Time Next Year, which records in February.
A source told The Sydney Morning Herald that the "final straw" was Karl and Jasmine Yarbrough's extravagant wedding in Mexico.
"It's no secret that the past year or so have been in many ways hard times for Karl, but I can say that every morning he's walked into this studio with energy and passion, and ideas to make the show bigger and better", Wilkins said.
"Peter has made a decision to explore new opportunities and is looking forward to spending weekends with his wife".
On Tuesday it was confirmed Sylvia's husband Peter was leaving Channel Nine after 15 years with the network.
"She (Stefanovic's ex-wife Cassandra Thorburn) has now signed up to do Dancing with the Stars next year, every week she's going to be on TV telling another sob story and that's going to make it impossible for Karl to claw his way back into public favour with the female audience".
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In March, Peter and Karl were embroiled in the Ubergate scandal after their private phone conversation in a taxi was leaked to New Idea magazine.
The Weekend Today host, 60 Minutes presenter and news journalist reportedly left by mutual agreement.
"I'm surprised by this", the source said.
The popular Channel 9 Adelaide newsreader is the hot favourite to take over the high-profile role.
"Nine's strength has always been in news".
The speculation about Karl Stefanovic's role as co-host has intensified in recent months and insiders claim it's a matter of when, not if, he's pushed.
"For over 14 years Karl has been at the centre of the Today Show bringing his unique personality and perspective to the day's news and current affairs".
Reports indicate Sylvia Jeffreys will be "redeployed" at Nine following the exits of Karl and Peter Stefanovic.