"You do that at your own risk. There's a number of advisers who have been extremely active on KiwiSaver. They are looking at cross selling other products. And they also know there's a fair chance some of those clients will come through the door one day with a lump sum to invest."

He also says advisers should target employers.

Surveys show employers are still confused about some aspects of KiwiSaver, suggesting there is a definite gap in the market.

There also seems to be an emerging preference for preferred providers, he says. More than 14,000 employers have taken this option.

Becker also gave advisers an idea of the scale of the KiwiSaver business.

ING's retail client base has doubled over the past 12 months, he says, and there are between 2000-3000 new clients a week – "mostly Kiwisaver."

Becker conceded ING had struggled to keep up with demand.

"From a retail distribution point of view I want to get as many KiwiSaver clients in as I can. But it has put a bit of pressure on some of our structure. We've had feedback our administration is not as good as it was."

Call centre traffic, usually requesting information packs and/or verbal information about KiwiSaver, has gone from an average of 2600 calls a week to 165,000 last month.

"A point you can take form this is you should have shares in a courier company or postal or paper company," Becker suggested, somewhat tongue –in-cheek.

"They're the ones making a lot of money at the moment."