The National Party has dropped below 30 per cent in a UMR poll, while Labour has reached as high as 55 per cent.

And when it comes to preferred Prime Minister, Jacinda Ardern has reached a near record-breaking 65 per cent approval rating.

Her popularity eclipses that of her National Party rival, Opposition leader Simon Bridges, who is on a mere 7 per cent.

It is understood the poll, obtained by the Herald, was conducted by Labour's polling company UMR for its corporate clients, who paid UMR for a monthly snapshot of the political scene.

The poll was taken between the 21st and the 27th of April - while the country was in the level 4 lockdown.

At 55 per cent, Labour would be able to form a government by itself.

But speaking to the Herald, Bridges rubbished the poll.

"UMR are Labour's pollsters and are consistently, badly wrong."

He added that Labour "should be focused on getting New Zealand back to work, not leaking dodgy numbers".

The UMR poll shows the Greens are on 5 per cent and New Zealand First – Labour's Coalition partners – on 6 per cent. The poll shows that the Act Party are on 3 per cent - its highest UMR poll rating since 2011.

National, however, is at 29 per cent in the poll – its lowest polled rating in more than a decade.

However, UMR warned that the political numbers should be taken with a grain of salt.

"They [the poll numbers] need to be interpreted extremely carefully. The conventional wisdom is that natural disasters (and wars) are usually good for governments but that those effects can wear off quickly."

The poll shows that National's Judith Collins and Bridges are neck-and-neck when it comes to preferred Prime Minister, both at 7 per cent.

Deputy Prime Minister Winston Peters is at 3 per cent.

And perhaps more good news for the Government – the poll shows that 78 per cent of New Zealanders believe the country is heading in the right direction.

The number of people saying New Zealand is on the right track hasn't been this high on a UMR poll since 1991.

"This can again only be attributed to a rallying around in a national crisis and a related current confidence in the government steps taken to combat Covid-19," UMR said in its commentary."

Polling under 30 per cent is a huge psychological barrier for National and means many of their current list MPs would lose their jobs at this year's election.

It comes as Bridges faces waves of criticism over his response to the Government's decision to extend the level 4 lockdown.

The criticism came from both his own MPs – leaking their frustration anonymously to media – and from his supporters, who rallied against him in a Facebook post with 30,000 comments.

Meanwhile, National MPs have been leaking information about a letter veteran MP Nick Smith sent to Bridges – in which he copied in the entire caucus – complaining about decisions made around the new Covid-19 policy committee.

Bridges said early this week that he would "absolutely" be National's leader come September 19.

He said he wasn't focused on leaks, but wanted to focus on the party's Covid-19 response.

At the same time, Prime Minister Jacinda Ardern has been praised both in New Zealand and overseas for her leadership during Covid-19.

The Financial Times called her "Saint Jacinda" and the Washington Post said that New Zealand was "squashing it".