Forget Russia, China or the United States, National leader Bill English has said that the biggest foreign influence on New Zealand comes from Australia.

In a briefing to incoming ministers, New Zealand's spy agencies warned of activities in the past year to attempt to access sensitive information or unduly influence expatriate communities.

While Australia worries about foreign influence from China and the US raises concerns about electoral interference from Russia, English said it is New Zealand's neighbours across the ditch who are most likely to be an influence.

At different times there have been concerns about influence from Russia, the US and China.

"I'm just saying if the concern is the influence of foreign countries on what happens in New Zealand then by far the most pervasive influence is Australia," he said.

English pointed at Australian-owned banks and insurance companies as a reason behind that influence.

Australia would prefer to regulate its own financial sector rather than have New Zealand do it locally, he said.

"That's a much more immediate offshore influence I think than any of the others."