Wellington: New Zealand's opposition Labour party is in disarray, following the resignation of leader Andrew Little just seven weeks before the country holds parliamentary elections.

Little said his decision was based on the party's disastrous performance in recent opinion polls.

"I do take responsibility and believe that Labour must have an opportunity to perform better under new leadership through to the election," Little said after a caucus meeting on Tuesday morning in Wellington.

Deputy Jacinda Ardern was announced leader of the Labour Party with Maori lawmaker Kelvin Davis elected as deputy leader.

"The situation we've found ourselves in is not want anyone expected or wanted," Ardern told reporters.

"We are determined and steadfast and I consider myself incredibly lucky to now call myself leader," the 37-year-old added.

Ardern joined the Labour Party aged 17 and has been in parliament since 2008. Earlier this year, she became Labour's youngest deputy leader and, at the age of 37, now becomes Labour's youngest leader.

A poll released on Sunday had showed Labour support at 24 per cent, while the Green Party had soared to 15 per cent. The governing National Party polled at 47 per cent support.

New Zealand is voting for a new parliament on September 23.

AAP