Wairarapa MP John Hayes is to step down at the next election, bringing to 10 the number of National MPs who have said they will go.
It is understood he has told Prime Minister John Key and has also written to his supporters in the electorate.
Mr Hayes, 65, was first elected MP for Wairarapa in 2005. That followed a career as an agricultural economist and then as a diplomat, including a stint as New Zealand's ambassador to Iran and Pakistan.
Before becoming an MP, he was best known for his part in the Bougainville peace process. He was made an officer of the New Zealand Order of Merit in recognition of that work.
He served as private secretary under former Labour trade minister Mike Moore and is currently parliamentary private secretary and chairman of the foreign affairs, defence and trade select committee.
His decision opens the way for multimillionaire investment banker Alastair Scott, who said he has thrown his hat in the ring.
Mr Scott is a former Credit Suisse First Boston managing director, who owns the Matahiwi Estate winery near Masterton.
He first indicated his interest in the seat before the 2011 election, but Mr Hayes refused to step aside then.
Mr Scott, who is a director of state-owned power grid operator Transpower, lives in Wellington and is on the council of Massey University.
"I have made it known to the party, to John and others . . . that I would seek nomination," he said.
He expected others would also express an interest in the seat.
Party insiders have drawn parallels between Mr Scott and leader John Key, who was headhunted for National after a successful career in international finance.
Mr Scott returned to New Zealand in 1997 after a stint as a top manager at Credit Suisse in London and Tokyo, where he said he was responsible for trading "derivative products in the Asian time zones".
- © Fairfax NZ News
Would you support your local council paying the 'living wage'?Related story: Council's living wage blowout