The Prime Minister has hit back at attention on whether he has financial interests with a firm that specialises in setting up foreign trusts in New Zealand.

John Key has a short term deposit with Antipodes Trust Group to cover the costs of a family trust.

Mr Key says he has no foreign trust interests and his deposit is handled by Antipodes Trust Group because his long-time personal lawyer moved to the firm.

"I don't deal with people unless they're highly ethical and they do things well. He's (Mr Key's lawyer, Ken Whitney) changed firms and that might get everyone else excited but from my point of view it's just situation normal," said Mr Key.

Asked if Mr Key would prefer that Antipodes Trust Group didn't advertise itself as being able to help out people wanting to set up foreign trusts here, Mr Key said, "There's a legitimate place, as I've been saying, for financial services when it comes to foreign trusts."

Addressing journalists after a business lunch in Wellington, Mr Key went on to say, "As you guys were very careful last night, I think, in your coverage of these matters; the reason you were is because you don't want to get your arses sued off you because actually they are a legitimate business. They're not the Devil incarnated.

"I mean, if a political party wants to say, 'I'm no longer going to have foreign trusts being allowed to be registered and supported in New Zealand' that's a call they can make. I mean, I think there'd be significant implications of that."

It has been estimated that foreign trust business earns New Zealand around $24 million annually.