New Zealand's prime minister Jacinda Ardern has announced she is stepping down ahead of this year's election, claiming to not have "enough in the tank" to continue.

Thursday's announcement comes at a time when polling shows her Labour Party faces a tough road to re-election in October, BBC reports.

Ardern said that the six "challenging" years as PM had taken a toll. She added that she had contemplated her future over summer, hoping to find the energy to continue in the position. "But unfortunately I haven't, and I would be doing a disservice to New Zealand to continue," she said on Thursday.

"I know there will be much discussion in the aftermath of this decision as to what the so called 'real' reason was... The only interesting angle you will find is that after going on six years of some big challenges, that I am human," she added.

"Politicians are human. We give all that we can, for as long as we can, and then it's time. And for me, it's time."

On Sunday, a ruling New Zealand Labour Party vote to choose a new leader will take place. This leader will be prime minister until the next general election, Reuters reports. Jacinda Ardern's term as leader will conclude on 7th February at the latest, and a general election will be held on 14th October.

Ardern said her government's accomplishments on social housing, climate change and reducing child poverty were ones she was especially proud of and concluded the news conference by saying: "As to my time in the job, I hope I leave New Zealanders with a belief that you can be kind, but strong, empathetic but decisive, optimistic but focused.

"And that you can be your own kind of leader - one who knows when it's time to go."

Prime minister of Australia, Anthony Albanese, said of Ardern: "Jacinda has been a fierce advocate for New Zealand, an inspiration to so many and a great friend to me." Whilst Canada's PM, Justin Trudeau, said she had made an "immeasurable" difference to the world.