Labour Party MP Shane Jones is quitting as an MP and politics altogether to take up a senior fisheries role in the Pacific.
Mr Jones is not expected to see out the rest of the term, and Radio New Zealand understands he will announce the date of his departure in the next few days.
He chaired the Treaty of Waitangi's Fishery Commission from 2000 to 2004, before entering Parliament as a list MP in 2005.
Last year, he unsuccessfully sought Labour's leadership after David Shearer stepped down, but lost to David Cunliffe. However, senior party sources said on Tuesday that he is leaving on good terms.
Party president Moira Coatsworth told Radio New Zealand's Checkpoint programme the decision hasn't come as a complete surprise and she was aware of the job offer.
Ms Coatsworth said she has spoken with Mr Jones about his future at various times in recent weeks. He confirmed his departure her on Tuesday and there is no ill-feeling among party colleagues, she said.
"I do want to say that Shane has been a really significant and respected front bench Labour member and he actually goes with our blessing and our thanks for what he has contributed to Labour."
Ms Coatsworth said she expected that Labour would keep good relations with Mr Jones.
Political commentator Matthew Hooton said he has been talking to Mr Jones off the record for a while and told Checkpoint it's clear that the MP has been unhappy with Labour.
"I think that Shane Jones has a particular view of what the Labour Party should be about, where it should be positioned in the political spectrum, and he doesn't feel that current Labour Party is positioned in that way as a sort of party for the working person."
Former MP Kelvin Davis is next on the party list and expected to replace Shane Jones.