A not-for-profit Kiwisaver provider says it's tough competing in New Zealand's banking market.

The Commerce Commission has today revealed the nation's banks are more profitable than overseas counterparts.

It's just released an initial review of those profits and plans to investigate whether a lack of competition is the problem.

Simplicity co-founder Sam Stubbs says most other OECD countries have open banking.

"Which opens the doors to competition. Four years ago, the Government promised that it would be here within 12 months. Four years later, it's still not here."

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