The latest survey from the Australian pollsters also shows bumper levels of support for minor parties, with Winston Peters' populist New Zealand First set for a sensational return to parliament.
A near-constant wave of scandal and distraction appears to be weighing on the Labour government, which switched leaders from Dame Jacinda Ardern to Chris Hipkins in January.
Support for Labour sunk to 26 per cent in Roy Morgan's July poll, down from 30.5 last month and well below their historic 50 per cent 2020 election result.
National-aligned pollster David Farrar said that result was "the lowest any governing party has been in a poll since November 1991" on Twitter.
In contrast, voters are liking what they see from centre-right opposition National, which rose 3.5 points to 33.5.
Roy Morgan chief executive Michele Levine said the result was "the lowest level of combined support for the governing Labour-Greens since they were elected to government in late 2017 nearly six years ago."
"The news in mid-June that New Zealand has officially entered into a recession appears to have knocked the wind out of Labour's chances of winning the election," she said.
Support for the two major parties fell again to a combined 59.5 per cent, suggesting voters are casting about for different ideas.
The highest-polling minor party is National's likely coalition partner ACT, a right-wing libertarian group, at 14 per cent.
Replicated into parliamentary representation, National and ACT combined would have 61 MPs in the 120-seat house.
Labour's caucus of 65 at the last election would be halved to just 33 MPs.
On these numbers, Labour would have two possible coalition partners: the Greens - which polled nine per cent or 12 MPs - and the Maori Party - with six per cent or eight MPs - for a total of 53 MPs.
New Zealand First has polled five per cent: right on the threshold to guarantee parliamentary representation under New Zealand's mixed-member proportional system.
NZ First governed with Labour in their first term before crashing out of parliament in 2020, and leader Winston Peters has vowed never to work with Labour again.
Mr Peters has courted anti-vax sentiment, railing against "bloated out-of-touch Wellington bureaucrats" and "woke sociological extremists" on the campaign trail.
The poll also brought good news too for self-described "radical centrists" TOP, which polled four per cent.
On these numbers, Raf Manji's party is just one per cent away from sending MPs to Wellington for the first time in its seven-year history.
Beyond the confirmation of a recession, Labour has endured a dour last six weeks, losing two ministers amid revelations of a divisive cabinet battle over tax policy.
As well as surveying party support, Roy Morgan also polls Kiwis on whether they think things are headed in the right or wrong direction.
In another marker of doom for the incumbent government, a record number now feel negatively about the future, with 29 per cent putting New Zealand on the right track, and 60.5 per cent on the wrong track.
Mr Hipkins remains chipper about his party's chances, offering a one-word answer on Monday when asked how many MPs he would have after the October 14 poll.
"Heaps," he said.
ROY MORGAN NEW ZEALAND JULY POLL
National - 33.5 (up 3.5)
Labour - 26 (down 4.5)
ACT - 14 (down 1)
Greens - 9 (down 0.5)
Maori - 6 (down 1)
NZ First - 5 (up 2)
TOP - 4 (up 1)
