New Zealand Labour MP Chris Hipkins, 44, who is currently minister for police, education and public service, is set to replace Jacinda Ardern as prime minister after becoming the only nominee for the party's leadership, reports indicate.

Hipkins was first elected to parliament in 2008. He was appointed minister for Covid-19 in November 2020.

In Ardern's shock announcement on Thursday, January 19, she said she did not have "enough in the tank" to lead.

Hipkins said succeeding Ardern as prime minister after her shock decision to resign amounts to "the biggest responsibility and the biggest privilege of my life."

"The weight of that responsibility is still sinking in," he told reporters on parliament's steps in Wellington on Saturday, in his first appearance since being nominated.

As reported, how long Hipkins will be in office is uncertain as New Zealand holds a general election in October.

He will need to be formally endorsed by the Labour Party in the House of Representatives on Sunday, January 22, before he can become leader.

If Hipkins receives that backing, Ardern will formally tender her resignation to the governor-general, who will then - on behalf of King Charles III - appoint Hipkins as prime minister.

Inflation and increasing social inequality saw Ardern's popularity fall to all-time lows according to opinion polls.