ACT Leader David Seymour says while he's comfortable as a private individual calling Russian President Vladimir Putin a war criminal, he's not as an MP.
Appearing on AM Early on Thursday, Seymour said the decision about whether Putin is a war criminal is up to a court to decide.
"You don't need someone to be a war criminal to attack them, there are lots of people in wars that are worth winning even if the person isn't a war criminal but let's also be clear, what I have said is I think he is a war criminal if you are asking David Seymour at home, yeah I think he is," he told AM.
"If you are asking me as a member of Parliament, then there is something we have got to respect here and that is a person is innocent until proven guilty in a court and that is very important because that is the difference between us and him.
Seymour has been impressed by the way the Western world has responded to Russia's invasion of Ukraine but said New Zealand cannot afford to be the "weakest link in the West".
"The world has changed and become a much more dangerous place …. and this country stands up for free and fair election and free speech and not murdering people," he told AM.
"Vladimir Putin is doing all that backed up with the implicit threat of using nuclear weapons, which is a very serious situation.
"The way the Western world has rallied including Australia to say look, we are on the right side of this has been so impressive and it's not just Governments, it's also businesses, it is also communities around the world. New Zealand cannot afford to be the weakest link in the west."
While stopping short of calling Putin a war criminal, he told AM the Government should still be providing Ukraine with weapons.
"New Zealand's military has a limited but useful number of weapons in particular the javelin missiles that have been so effective against Russian tanks.
"ACT said almost three weeks ago now, we have got 24 of these launchers, we have a couple hundred of these missiles, there are no Russian tanks in New Zealand right now so maybe we should send them to the people who are desperately defending their homes and their democratic way of life."
It comes after shocking images were published this week which showed bodies strewn over the streets of the Ukrainian town of Bucha, which was until recently occupied by Russian forces.
The United Nations High Commissioner for Human Rights Michelle Bachelet said the reports raise "serious and disturbing questions about possible war crimes". US President Joe Biden said it is a "war crime", while Ukrainian President Volodymyr Zelensky described it as a "genocide". Russia has denied all accusations.
In New Zealand, National Party leader Christopher Luxon is "comfortable" calling Putin a "war criminal", Prime Minister Jacinda Ardern said his actions were "beyond reprehensible" but refused to explicitly call him a "war criminal" while Greens co-leader James Shaw said he is a "ghastly, ghastly human being".
The United Nations said 11 million Ukrainians - more than a quarter of the population - have fled their homes while more than 4 million of those people have left Ukraine.