When he was National's finance spokesman in 2005, he spoke to the Herald about New Zealand becoming the "Jersey of the South Pacific" and his wish to develop the offshore banking industry.
Jersey, a tiny British Crown dependency off the coast of France, is a popular tax haven because its light taxes. Half of its economy comes from financial services.
Asked about the comments today, Mr Key said there was no reason New Zealand could not develop an offshore banking system if it followed strict international rules on tax and compliance.
"I think there's a role for New Zealand to play in providing financial services," he said.
"We ... have very strict obligations around disclosure and we meet those obligations."
New Zealand's disclosure regime for foreign trusts set it apart from the well-known island havens, he said.
Mr Key has said New Zealand should position itself as an Asia-Pacific "Switzerland" and attract high net worth individuals.
When the Panama Papers made global headlines on Monday, Mr Key was forced to defend his vision to model New Zealand on a country known for its secretive financial system and tax haven activity.
Switzerland was "going through a significant change in terms of its disclosure regime", he said.
"From New Zealand's point of view, we've got all these tax treaties, we disclose information where it's required in terms of trustees, and other countries can follow that up."
Labour's finance spokesman Grant Robertson raised Mr Key's past comments on tax havens in Parliament today.
"That's not the economy that we want in New Zealand," he said.
"We want an economy in which people aren't serving coffee to the 1 per cent, that we're actually making and building the things that will help people have a share in prosperity."
The value of accountancy fees and other costs related to the 12,000 foreign trusts in New Zealand has been estimated at $24 million.
Green Party co-leader James Shaw said this income was not worth the reputational risk related to the trusts.
