Former National Party leader Don Brash says there is not a lot Simon Bridges can do about Judith Collins beating him in the polls. 

The latest Newshub Reid Research Poll shows National has dropped to 41.6 per cent, while Labour is up to 47.5 per cent. 

In more bad news for National, only five per cent prefer Bridges as Prime Minister, compared to 6.2 who want Judith Collins in the top job.

Don Brash told Mike Hosking Simon Bridges is in an uncomfortable position.

"I'm sure he is worried. It's a very uncomfortable position for him to be in [there's] no doubt about that."

"He has in the past, pointed out that Helen Clark polled single digits, and indeed, low single digits when she was leader and came back, of course, to almost win the 1996 election," he said.

"I don't think he will be absolutely paranoid but no leader would find it comfortable having someone in his caucus ahead of him."

However, Brash said there isn't much Bridges can do about it. 

"One of the things helping Judith Collins a lot is the total muck up of KiwiBuild. That's one of the Government's weakest point and she is responsible for the housing portfolio on the National side so she has got lots of profile."

He said it isn't surprising that Prime Minister Jacinda Ardern has moved up the polls so strongly.

"She was in Davos, she got the international press, everyone loves her so her increase isn't surprising."

However, Brash said both the Green Party and NZ First are hovering in dangerous territory.

"The Greens are hovering right on the margin just over five [per cent] and, of course, NZ First is well under five [per cent], both those parties could be wiped out in the next election."