Victorian MP Sam Groth announced in early January he would quit as the party's deputy leader and not recontest his seat of Nepean on the state's Mornington Peninsula at the state election in November.
The former tennis ace has since decided to pull the pin next week to pursue "other opportunities", triggering a by-election.
In a statement, Mr Groth said it had been an honour to serve the people of Nepean.
"I am very grateful to my staff for their professionalism, dedication and tireless work in supporting the people of Nepean," he said.
He wished Opposition Leader Jess Wilson and the party the "very best" for the November election.
"Most importantly, I thank my family, my wife Britt and our twin boys, for their unwavering love and support."
Mr Groth previously revealed party infighting and public pressure on his family had become unbearable.
The 38-year-old and his wife, Brittany, settled legal action in November with one of Australia's biggest newspapers.
Mr Groth sued Melbourne's Herald Sun newspaper over articles published in late July relating to when the pair began their relationship.
During the court process, it was revealed a Liberal MP had contacted the outlet with a "piece of gossip".
Mr Groth was not in Victorian parliament's lower house for question time on Wednesday afternoon.
Premier Jacinta Allan alluded to Mr Groth's decision, thanking Ms Wilson for "volleying" a question at her.
Mr Groth's life in politics followed a tennis career that included a world record fastest serve in 2012 and a career-high ATP singles ranking of 53 in 2015.
He reclaimed the then ultra-marginal seat from Labor in 2022 on a margin of more than six per cent.
In late January, Liberal stalwart David Southwick won a vote to replace Mr Groth as deputy leader over backbencher Chris Crewther.
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