Minor parties could be a thing of the past when it comes to next year's election.

A new Reid Research poll was commissioned by Business NZ, intended to gauge public support for capital gains tax, has shown minimal support for the smaller parties. 

The poll began on March 15, the same day as the terror attack, and ran until March 23, two days after Ardern announced the detail of gun reforms at her post Cabinet press conference.

As part of it, the 1000 polled were also asked which party they supported.

Once those who did not give a choice of party are taken out, Labour was on 49.6 per cent, National on 41.3 per cent and NZ First and the Green Party were languishing on 2.3 per cent and 3.9 per cent respectively.

In the last Newshub Reid Research poll from February, Labour was on 47.5 and National was on 41.6 per cent.

National leader Simon Bridges did not address the drop in support for his party, but told The Country host Jamie Mackay that it could be a two-horse race.

"I think there will be a bit of truth to that, both those minor parties being under five per cent."

The five per cent threshold is what parties currently need to get into Parliament. 

"I think New Zealand First has got some issues. They backed a left-wing horse, I don't think their voters really wanted that," Bridges says. 

He says that voters also did not want them to back an oil and gas ban or money for overseas diplomacy. 

"That's coming through not just in this poll, but over the last year that's been a common theme."