The 1News Colmar Brunton poll showed Labour had risen 6 points to 43%, while National had fallen three points to 41%.
Labour leader Jacinda Ardern also leads the preferred Prime Minister poll, rising 4 points to 34%. National leader Bill English rose three points to 33%.
New Zealand First leader Winston fell 3 points to 4%.
Despite the surge in the polls, Labour could now form a government with just NZ First as a coalition partner. It could not get over the line with just the Greens.
The embattled Greens rose 1 point to make the crucial 5% threshold. NZ First fell two points to 8%.
The Opportunities Party fell 1 point to 1%, while Maori Party also fell 1 point to 1%. No other parties were in the picture.
Labour has now risen 19 points in the four weeks since Ms Ardern took over as leader.
It is the first time Labour has polled higher than National since 2006, when Helen Clark was in charge.
The previous poll in mid-August showed National on 44% and Labour on 37%.
Mr English and Ms Ardern were neck-and-neck in the preferred Prime Minister stakes in the last poll, on 30%.
In the lead-up to the latest poll, Labour officially launched its election campaign at the Auckland Town Hall.
Ms Ardern announced new policies including free tertiary education, cutting GP costs to $8 for half of New Zealanders, and construction of a $1 billion hospital in Dunedin.
National launched its campaign on Sunday, announcing an education package which included funding to allow all schoolchildren to learn a second language, improvements to maths teaching at primary level, and digital learning at secondary schools.
Leader Mr English has also announced four more weeks of paid parental leave and $10.5 billion on seven new highways around New Zealand.
National was also accused by Winston Peters of leaking details about his superannuation payments, though it is not known whether this fell within the polling period.
Labour has risen dramatically in the polls since Ms Ardern became leader. Before she replaced Andrew Little, Labour's result in the same poll was 24%.
The general election will be held on September 23.
