Ansvar says about 1000 customers in Canterbury could be without private earthquake insurance when the company withdraws from the New Zealand market on Saturday.
Ansvar Insurance says it faces $700 million of earthquake claims but only $35 million in premiums.
The claims will all be covered by reinsurance and capital.
The company says it has just over 10,600 New Zealand clients - about 1500 of them in Christchurch.
The company's Australasian chief executive Andrew Moon says some direct Christchurch customers have been offered earthquake cover, under a deal with Lumley Insurance.
But he's aware of other, brokered, customers - now with other insurers - who have no private earthquake cover.
Mr Moon says withdrawing from the market has been the hardest decision he's ever made but continuing to do business in New Zealand was no longer economically viable.
He believes the company has done its best to help clients find new insurers.
