Labor's Bastian Seidel says his brief time in Tasmanian politics has left him bitter and sad.
The upper house member on Monday announced he would resign at the end of the year - just one year into his six-year term in the Legislative Council.
Dr Seidel said he wrote to Labor leader Rebecca White on Sunday night and offered his resignation from the Labor caucus and shadow health portfolio.
"The problems in the Labor Party are obvious," he said.
"I have tried to work constructively to solve some of our issues in our party, but have come to the realisation that I have failed.
"I can't work in a toxic environment and I can't work with people who constantly leak information to the media out of pure selfishness.
"I've been quite clear to my colleagues in caucus that when we have debates and discussions in the party room, they are meant to be confidential.
"It's not extraordinary to expect that.
"To think after last night, when there was almost a live newsfeed straight from the caucus room, it's not a working environment."
Dr Seidel said unlike others, he did not enjoy political infighting.
"It is sad and depressing and too often I felt like I was a dispensable pawn in somebody else's stupid game," he said.
"In my brief time in politics, it's just left me disillusioned and I'm bitter and I'm sad.
"There's got to be virtue in politics, but I just cant see it, and for that reason, I have decided to resign."
Dr Seidel said problems within the state Labor Party began to emerge around the Christmas break.
Dr Seidel said he would leave Parliament on the final sitting day on December 3.
He said he did not want to leave the party to serve as an independent in the Legislative Council.