Victorian Liberal MP Edward O'Donohue will quit state politics within months, after a discussion with the party's new parliamentary leader, Matthew Guy.
In a statement on Twitter, Mr O'Donohue said he had already told former leader Michael O'Brien he won't contest the 2022 election.
But Matthew Guy's return to the helm last week has prompted the upper house MP to bring forward his exit from parliament.
"It's the right time to let Matthew Guy choose a shadow cabinet that he can take to the next election," Mr O'Donohue told reporters on Saturday.
"I wish Matthew and the team nothing but every success at the next election in just over a year's time."
Mr Guy is expected to unveil his shadow cabinet on Sunday, with a focus on COVID-19 recovery.
He led the coalition to a crashing defeat at the 2018 election, which saw the party shed 10 of its 37 lower-house seats including blue-ribbon Hawthorn.
Discontent with the Labor government's tough lockdown restrictions could see him make up some ground in 2022.
Mr Guy paid tribute to his long-time colleague, describing Mr O'Donohue as one of the "gentlemen of this parliament".
"He is one of the finest individuals in this building, he is just a lovely person, genuine, honest, one of the smartest in our team," he said.
Mr O'Donohue, 47, was first elected in 2006, and voters returned him to parliament at the following three elections.
He was a long-time member of the Liberal shadow cabinet and served as corrections minister in 2013-14.
The eastern region MP said he was pleased the broad reforms he initiated to the parole system, after the deaths of several women at the hands of parolees, had "stood the test of time" and made a difference to community safety.
He was coy about whether the party should choose a female candidate to replace him, but said it was important the Liberals "reflect the community we seek to serve".