Labour leader Andrew Little has slapped down Green Party co-leader James Shaw's comparison of US President Donald Trump to Adolf Hitler, saying the first person to bring Hitler into an argument had lost it.

Shaw said Trump was "the most dangerous person since Adolf Hitler" on TV show Backbenches on Wednesday night as part of a panel of politicians.

ACT Party leader David Seymour said it was the sort of hyperbole you'd expect from Trump himself.

Andrew Little said people needed to keep things in perspective and have a little faith in the US system.

"Pretty much I follow the principle that the first person to raise Hitler in a political argument loses it.

"Just keep things in perspective. The US is a long-standing democracy. It has a constitution that has very strong checks and balances -some Americans say too many, because things can't get done.

"But it is a strong, solid democracy and when things do kind of bust out, it has a way of bringing them back in."

He said some of the recent reported developments on Trump were worrying.

"I think the world can see a US President who is unrehearsed in the rigours of government coming to terms with that. The main thing is to make sure that doesn't put either that great country or the rest of the world at undue risk.

"But I trust the American political establishment ultimately to have enough checks and balances to prevent that from happening."

Shaw said he accepted it was not an appropriate comparison.

"I said that in the context of a pub politics show and I was being hyperbolic, and it wasn't really an appropriate comparison.

"However, I do think Trump has the capacity to plunge the world into chaos. The US does have safeguards, which he is testing at the moment."

Little's comments come as talk of impeachment swirls in the US following reports Trump had given sensitive intelligence to Russia and had asked former FBI head James Comey to halt an investigation into Michael Flynn, Trump's former National Security Adviser.

Little said Trump's "alleged security infidelity" was just one of an ongoing catalogue of issues.

"It is starting to feel somewhat Nixonian, if I could put it that way, that you have a President who seems to not respect some of the basic rules of government and being in government, and being head of state of the most powerful country still in the world.

"We need to have a stable US and a stable US Administration. So I have to say it is starting to feel a little worrying, what is happening in Washington at the moment."

He doubted any instability would destroy the Five Eyes intelligence partnership, something he said had survived "all sorts of governments".

"But if intelligence gathered through Five Eyes partners is wrongly used, and in this case by the President of the US, it certainly reduces trust in the sharing of information. And it may just be that the partners have to conduct that security and intelligence relationship in a different way while that risk remains."

- NZ Herald