Prime Minister John Key has insisted Britain is stronger as part of the European Union in an intervention his British counterpart David Cameron labelled "important".
Key said his country would be looking to join the EU rather than leave it if the trading bloc was on the Pacific nation's doorstep.
Britain will hold a referendum later this year on whether or not to remain with the 28-country European partnership.
Key spoke out after he met Cameron on the margins of a nuclear security summit in Washington.
"We certainly think it's a stronger position for Britain to be in Europe," he said.
"We see Europe as an extremely important continent that needs strong leadership. We think Britain provides that leadership.
"We are currently going through the process of wanting to sign a free trade agreement with Europe because it is the home of 500 million people and a huge amount of middle income consumers.
"As someone who has lived in the United Kingdom for a long period of my working life, I guess all I would say is that if we had the equivalent of Europe on our doorstep, New Zealand as a country would be looking to join that. We certainly wouldn't be looking to leave it.
"But the British people will make up their own minds what they think is appropriate and they will vote accordingly."
Cameron said the comments made by his New Zealand counterpart were "important".
