Wellington: Former New Zealand prime minister Helen Clark has forged a formidable reputation in her homeland, with political allies noting her “steely determination” as she bids to become the first woman to lead the United Nations.

Clark, who on Monday announced her candidacy for the UN secretary-general’s role after months of speculation, led New Zealand’s centre-left Labour government for three successive terms from 1999-2008.

The 66-year-old then went on to head the UN’s largest agency, the UN Development Programme (UNDP), making her the highest-ranking woman at the world body.

“She is the best person for the job,” New Zealand Prime Minister John Key, who succeeded Clark, said in announcing her candidacy in Wellington.

He said Clark was a proven leader, adding: “It isn’t just the time Clark spent as PM, her entire life has been dedicated to foreign policy.”

Born into a conservative North Island farming family, she became involved in politics through the Vietnam War protests and her opposition to rugby tours to apartheid-era South Africa.

Clark was first elected to parliament in 1981 and quickly rose through the ranks, becoming deputy prime minister in 1989 as the Labour government was imploding over controversial economic reforms.

It was ousted in 1990 and Clark took over as leader in 1993, struggling to unite an opposition party that was demoralised and riven by ideological disputes.

With her opinion poll rating as preferred prime minister at a record low of two per cent, Clark dug in and refused to stand down when party power brokers told her to go.

Her refusal to buckle in the face of seemingly overwhelming odds was rewarded when she won office in 1999.

Her administration was initially dismissed by critics as “Helengrad” due to her tight grip on the reins, but Clark’s style eventually became more moderate and pragmatic.

But she retained an independent streak, breaking ranks with Australia, Britain and the United States when she refused to send troops to the war in Iraq.

With strong popular support, she has also maintained the country’s nuclear-free status, which was introduced by Labour prime minister David Lange in 1984 and soured relations with Washington.

She cites Nelson Mandela as her biggest political inspiration and questioned in 2013 about her achievements as prime minister replied: “I believe that as PM I contributed to making NZ a fairer, better place to live in.”

She also said the move from Wellington’s parliament to UN headquarters in New York had not changed her management style: “Stay on top of the issues, and be proactive and inclusive,” she said.

Clark’s successor as Labour leader, Andrew Little, said she was more than capable of handling the UN’s top job.

“Renowned for her steely determination and formidable capabilities, she would make an excellent secretary-general,” Little said.

“She is, and always has been, a trailblazer.”