Former Olympic athlete and fill-in presenter Matt Shirvington has been elevated to host alongside Natalie Barr.

The "worst-kept secret" was announced on air on June 5 with "Shirvo" admitting he was more nervous than at the Olympics - where he represented Australia in 2000 - to be taking on the role.

"[The show] is a mouthpiece for all Australians and their stories," he said.

"The thing I love most is sitting on this couch going from complete elation and excitement and happiness with some of the stories you hear about, to the heartbreak and horror and sadness, wiping a tear from your eye and moving on."

Mr Shirvington said it was an "honour and privilege" to be named the new co-host with his first official show on June 12.

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It follows Mr Koch's announcement he was leaving the program after 21 years.

In an emotional on-air speech on May 29, Mr Koch said he was stepping away to focus on other pursuits including his role as president of Port Adelaide Football Club.

"I have loved every single minute of it and I'm incredibly proud of what we've achieved here over the last 21 years," he said.