Simon Bridges is likening New Zealand's free trade negotiations with the United States to a "fly" dealing with an "elephant".
Prime Minister Jacinda Ardern insisted in Melbourne last week that any free trade deal with the US "must always be on our terms".
Bridges branded Ardern's tough stance unrealistic, telling Magic Talk: "I'm sorry, but when you're dealing with an elephant and you're a fly, you've got to have a little respect for the elephant."
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Bridges, leader of the National Party, said Ardern needs to focus more on boosting New Zealand's economic position - like pursuing free trade with the US - rather than delivering speeches.
"We'll never get [free trade with the US] when you've got a Prime Minister that's more concerned with TED Talk's in Melbourne than what's in New Zealand's core interests such as our trade relationships overseas."
His comments followed the Prime Minister's trip to Melbourne where she met with Australian Prime Minister Scott Morrison, and also delivered a speech in which she warned against "heavily nationalist agendas".
Ardern called on the US to play a larger role in Asia-Pacific in her speech to the Australia New Zealand School of Government, accusing the superpower of not paying the "same level of attention" in the region that Australia and New Zealand had.
While the Prime Minister had stern words for the US, Foreign Minister Winston Peters was in Washington, DC, trying to secure a Free Trade Agreement (FTA) in a face-to-face meeting with US Vice President Mike Pence.
When asked in Melbourne if she supported Peters' pitch for free trade with the US, Ardern said New Zealand is continuing to fight against US tariffs on aluminium and steel, and said any FTA would need to "equally serve New Zealand's interests".
"That includes protecting Pharmac; protecting our right to regulate and protecting the Treaty of Waitangi."
Bridges said New Zealand has "no chance" of getting an FTA with the US if the Prime Minister won't visit the superpower, instead sending the Foreign Minister.
"We've got massive tensions in the US-China relationship and I just don't know where our Government stands on them because Winston and Jacinda are at odds on it - one's woke and one's the opposite."
Ardern voiced her opposition to nationalist regimes at the United Nations General Assembly in New York last year.
She doubled down on her anti-nationalist stance in Melbourne, saying Australia and New Zealand could be "examples to the world" of what it looks like to prioritise international rules and norms "that work for all countries".
While in New York last year, Ardern said she discussed exempting New Zealand from US steel and aluminium tariffs with President Trump, but the tariffs on exports to the US remain.