IAG, which owns AMI Insurance, State, and NZI, is raising car insurance excess by 25 percent due to rising costs, it says.
All new policies or renewals would have the standard excess on car claims raised from $300 to $400.
The Australian-owned company said it was spending more paying out on claims than in the past.
It said raising the excess, rather than premiums, meant rising costs were being met by claimants rather than everybody who had an insurance policy.