Health Minister Tony Ryall will retire from politics at the next election to take up employment in the private sector.
Mr Ryall, 49, has been a key figure in the National Government and is widely credited for a stable watch over the health portfolio, introducing changes without causing controversy.
His retirement announcement was unexpected and he will remain in Cabinet until the election. He said it was the right time for him to leave, but he had "greatly enjoyed" being in Parliament.
"The Government is doing very well and the National Party is in great heart."
He said he had told the Prime Minister and Deputy Prime Minister Bill English, who were "disappointed but supportive."
He said he was proud of his work as Health Minister, especially in the areas of elective surgery, faster cancer treatment, and preventive health care.
"Our health services have been transformed with a great effort by clinicians and motivated teams across the sector .. My more business-like approach has provided more services and better care for patients within a tight budgetary environment."
He said that as State Owned Enterprises Minister, he had also enjoyed working with Mr English to oversee the government share offer programme, and working on the strategies to cap public service staff.
"There is still a lot of work to do in both my portfolios and I appreciate the Prime Minister allowing me to continue my work in Cabinet until the next election."
National Party President Peter Goodfellow said Mr Ryall would leave a legacy few could match.
"Tony will leave at this election with the respect and admiration of colleagues and his opponents alike. I wish him and his family well for whatever new opportunities lie ahead."
Mr Goodfellow also paid tribute to Mr Ryall for building up an 18,000 vote majority in the Bay of Plenty electorate, saying it had the second highest party membership of any electorate.
Northland is the highest.
Labour's health spokeswoman Annette King was less glowing about Mr Ryall's efforts in the health portfolio, giving him an "A for politics, but a 'barely achieved' for health."
She said his greatest work had been in closing down critics and the bad news in the health portfolio.
"He has been too controlling, divisive and created a climate of fear. He should go not and let someone else try to repair the damage in relationships."
She said a recent poll of doctors showed he was increasingly unpopular.
"Minister of Health is a tough job so I understand him leaving although I'd like the job back!"
Tony Ryall biography:
Mr Ryall entered Parliament as MP for East Cape in 1990, aged 26. He was one of the four young ministers in National's so-called 'Brat Pack' of the late 1990s, along with Bill English, Nick Smith and Roger Sowry. He is now the MP for Bay of Plenty. He is renowned around Parliament for his flamboyant shirt and tie combinations.
He was first made a minister under the Jenny Shipley National Government in 1997, holding the portfolios of Justice, State Owned Enterprises, Local Government, Youth Affairs and Housing New Zealand Ltd.
He is married with two children.