The centre-right party was destroyed in Jacinda Ardern's Labour landslide on Saturday, shedding 18 per cent from their 2017 result and, likely, 19 MPs from their party room.

Deputy leader Gerry Brownlee was one of the losers, ceding his Christchurch-based seat of Ilam to Labour's Sarah Pallett despite holding it for 24 years.

"We've had a shocking year. An absolute shocker, right from the start," he told TVNZ.

National has lurched from crisis to crisis during 2020 after starting the year in an election-winning position.

Simon Bridges was rolled as leader after a tone-deaf response to COVID-19, criticising Ms Ardern's response when many New Zealanders wanted unity in the face of the pandemic.

His successor, Todd Muller, stunned many by installing a front bench without any Maori, then by standing down after less than two months due to mental health.

With just weeks until the election, the party turned to Ms Collins, but in hindsight it appears an election they were bound to lose.

National's primary question is whether to stick with Ms Collins - who publicly gave herself a 35 per cent as a pass mark - as leader.

With special votes still to be counted, which National traditionally does badly in, the party sits at just 26.8 per cent.

"Judith was was put in an awful position," Mr Brownlee said.

"I believe (she should stay).

"It would be totally the wrong thing at the moment to head down a track of of leadership discussion."

Mark Mitchell, who stood against Ms Collins for the leadership, also backed her to stay.

"I'm not going to challenge Judith Collins for the leadership," he said.

"Judith had a very tough job and in my view she worked very hard ... (challenging) is the furthest thing from my mind."

Mr Brownlee will stay in parliament as a List MP, but has foreshadowed stepping away, saying "I'll think about over the next few days".

Australian Associated Press