Simon Bridges to be gone by July, Paula Bennett not far behind - Winston Peters

Simon Bridges will be gone as National Party leader by July, according to Winston Peters - and Paula Bennett won't last much longer.

The Deputy Prime Minister spoke to Magic Talk's Brendan Telfer on Wednesday afternoon, just hours after Jacinda Ardern announced her Government had ruled out implementing a Capital Gains Tax (CGT).

Opposition leader Bridges has said his party's "relentless opposition" to the CGT forced the Government's hand, but Peters has quite a different view.

"This man has been praying five times a day that we'd go with the Capital Gains Tax," he said.

"But now his death knell has been announced at 2 o'clock today, and he won't, in my view, make it as leader by the time of their next conference in July.

"That's the blunt fact, and politics is something I know a little bit about."

He said Bridges simply doesn't have the credibility to claim responsibility.

"If I was to ask your drive time listeners to toot their horn if they believe him, there would be utter silence. If I were to ask them to toot their horn if they don't believe him, the noise in Auckland would be deafening and even in Invercargill and Kaitaia too."

In the latest political poll conducted by TVNZ and Colmar Brunton, Bridges' preferred Prime Minister rating slipped down to five percent - the lowest he's ever polled as party leader.

Newshub has been told of agitation behind the scenes of the National Party, with several anonymous MPs speaking out against their leader. Peters is confident a leadership challenge is in sight - and Bridges won't make it out alive.

"He's on his last legs. I'm sorry because he's not a bad bloke, but he doesn't cut it. And if he can only get five of 40 National voters to think he's the man for the job, he's got a serious problem.

"We've been hearing the acute sounds of the grindstone working while knives have been sharpening - even on the seventh floor of the Beehive."

When asked who will replace Bridges if he is ousted, Peters said National "haven't got many options".

"First they'll come for Paula Bennett because that's the way they are in the National Party. Then Simon's goodnight nurse and they'll have a new team lined up, but they won't have the thing that really matters - a person who is a leader. They don't demonstrate having one at the moment."

Judith Collins has long been rumoured to be considering a tilt at the leadership, and she's polling higher than Bridges. But Peters isn't intimidated by the prospect of Crusher Collins as Opposition leader.

"Bring it on. As Rafael Nadal the tennis player says, who's next? The fact is we're going to get on with running this country and running it for the better."

The Deputy Prime Minister defended the Government's decision not to go ahead with the CGT, saying although New Zealand's tax system is clearly unfair, the CGT wasn't the right move to remedy it.

"The reality is you should always look at whether circumstances and facts have changed with respect to any taxation, and in this case it was our view the facts hadn't changed.

"Installation of this tax in offshore jurisdictions had not dealt through the problems they claimed the tax would. There have to be better ways of ensuring a fairer tax system.

"To pick a blunt instrument like a Capital Gains Tax, with all its complexity, was a mistake in our view," he added. "A mistaken option, and so we didn't go for it."

Peters said the public would be mistaken in thinking there's now tension between New Zealand First and Labour over their inability to come to an agreement.

"We've had a long arduous consideration of that matter. We've given it our best shot, but on this issue we can't get agreement. It's better to be honest, straight up-front, than bitterly resentful while you're making an unacceptable compromise."