A National Party member has called the election "a catastrophe", while TVNZ presenter Hilary Barry agreed, saying the party is having a "horrific night".
Liam Hehir, who is providing analysis for TVNZ's election night coverage, said National expected to have a “rough night” but this is worse than expected.
"Catastrophe - there is no other word for it. This is a 2002-level result, the difference being the party vote is a little bit higher because there is nowhere else to go.
"There is no United Future, no New Zealand First to speak of anymore for it to pick up some of the vote. So National voters or people who habitually vote for National can go to ACT, and they have, and that’s why they are doing so well.
"I don’t think it’s how good ACT have been - I think it’s National voters jumping ship and a lot of people going to Labour," he said.
"We expected it to be bad but this is in the worst range of possibilities. It’ll be very disappointing for National."
His analysis comes as National is currently sitting on just 25.8 per cent of the vote at the time of writing.
Labour is nearly double that at 50.5 per cent of the vote.
The Greens and ACT join Labour in having a strong showing, with both parties expected to pick up more seats in Parliament than at the last election.
NZ First, however, is languishing well below the five per cent threshold with TOP, New Conservatives and the Māori Party.