Victoria's former trade minister Philip Dalidakis has quit state parliament, saying he is no longer "all in" to do the job.
The upper house MP, who did not stay in cabinet after Labor's return to government last year, announced on Facebook on Monday he would immediately step away from politics.
"Since stepping down from the ministry six months ago, I have had more time with my family, more time in my community and more time to reflect on my priorities and what I want to achieve and what I want to do," he wrote.
"If you are to do this job, you need to be all in. I can no longer say that I am and so it's time to pass the baton onto someone that is."
Mr Dalidakis will join Australia Post at its Melbourne headquarters from July 1, The Age reports.
His departure will create a casual vacancy for the government in the legislative council and the party will decide who will fill it.
The government is this week trying to pass controversial firefighting reforms through the upper house and Mr Dalidakis' resignation will create a delicate voting balance for it in that chamber, because it was already relying on three crossbench MPs to help legislation get through.
Premier Daniel Andrews said in a statement he wished his former minister the best for the future.
"I want to thank him for his service, particularly during his time as minister for small business, trade and investment, and the digital economy, and most recently as chair of the Public Accounts and Estimates Committee," he said.
Australian Associated Press