Queensland Labor deputy leader Tim Mulherin has announced on day four of the state election campaign that he will quit politics.

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The veteran MP will not re-contest his north Queensland seat of Mackay at the polls in three weeks.

The ALP holds the seat by a narrow margin of 0.5 per cent.

Mr Mulherin made the decision to retire on Thursday evening, after health and family issues became too great.

His father Leo died late last year and he has been looking after his mother.

The family death also led to Mr Mulherin delaying cardiac surgery.

He flew back into Mackay airport early this morning as news of his retirement filtered out.

Standing alongside Mr Mulherin in Mackay on Friday morning, Labor leader Annastacia Palaszczuk named Julieanne Gilbert as the party's new candidate for Mackay.

"I have informed Evan Moorhead the [Labor] state secretary this morning of my decision, after discussions with Tim, to put forward Julieanne as a strong journal representative for this area," she said.

"Julieanne was born and bred in Mackay.

"She is passionate about education. She has been a primary schoolteacher for over a decade and she now advocates for teachers' interests right across this state.

"Julieanne will hit the ground running and she will be a very strong, local candidate for the seat of Mackay."

Earlier today, Mr Mulherin became emotional as he reflected on an "exciting" career.

"I've had a great relationship with Annastacia," he said.

"I met a lot of people that certainly had a huge influence on me.

"You know, I'll miss a lot of people. I've got friends on all sides of politics.

"The people of Mackay have been good to me, I hope I've been good to them."

Ms Palaszczuk said Mr Mulherin would continue on as deputy up until election day.

"Tim Mulherin has been part of this journey over the last three years," she said.

"He has been my right-hand man and he has been with me through thick and thin over the last three years."

Premier Campbell Newman noted Mr Mulherin's departure and offered his best wishes.

"He is an experienced member of the Labor team and it is quite unexpected but I extend my best wishes to him for the future," Mr Newman said.

"But this election is not about individuals, it's about who has a strong, united team with a strong plan for Queensland.

"We have that and the Labor Party do not."

Mr Mulherin was elected in 1995 and was one of only seven Labor MPs to scrape through in the 2012 election whitewash.

He had served as minister for primary industries and fisheries and agriculture minister under the Beattie and Bligh government and was promoted to deputy leader under Ms Palaszczuk.

Together, they helped rebuild the Labor Party, which is now in striking distance to win the election.

"He is a gentlemen and scholar," Ms Palaszczuk said.

"I have never met anyone who was more engaged with their community.

"He will go down in history as Mr Mackay."