Sam Groth, the party's deputy leader in Victoria's state parliament, confirmed on Monday morning that he will not contest his seat of Nepean at the 2026 state election.
"After many conversations with my wife and with a great deal of personal thought, I have informed the Leader of the Opposition that I have decided that I cannot continue in parliament beyond the election," he said.
The announcement comes months after the senior Liberal MP and his wife, Brittany, settled legal action 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 legal process, it was revealed a Liberal MP had contacted the outlet with a "piece of gossip".
Mr Groth on Monday said the public pressure placed on his family over the recent months had been significant.
"Realising that some of it came from within my own party has been difficult to ignore. Coming to that realisation has forced some very personal reflection," he said.
"I have always tried to approach this job with honesty, hard work and a clear focus on the people who put their trust in me. But when you find yourself having to fight against your own team, it becomes impossible to put those interests first.
"That is not the standard I came into public life to accept, and it is not the kind of politics Victorians deserve."
Mr Groth described the past few months as an extremely challenging period for his family.
"We took on this role for the right reasons, to contribute to our community and try to make a positive difference. That purpose has never changed, but the environment around it has," he added.
In May last year, Mr Groth made headlines after using then-opposition upper house leader Georgie Crozier's chauffeur-driven vehicle to get home home from the Australian Open in January 2024.
He had earlier hosted a political fundraiser with Nationals MP Jade Benham, adding it was important to meet stakeholders and attend meetings.
The 38-year-old's stint in politics followed a storied tennis career, which included a world record-breaking, fastest-ever serve in 2012 and a career-high ATP singles ranking of 53 in 2015.
Mr Groth was elected to the seat of Nepean, which covers the southern part of the Mornington Peninsula, in Victoria's 2022 election.
The Liberals reclaimed the ultra-marginal seat from Labor, which had held it by under one per cent.
The former tennis star will take time to consider what comes next and the opportunities ahead.
It's unclear whether he will continue as the deputy leader.