Westpac New Zealand is to remain part of the Australian-owned Westpac Group.
The Australian parent decided to keep the New Zealand business following a detailed review.
Westpac Group chief executive Peter King said a demerger of the New Zealand business would not be in the best interests of shareholders.
He said the bank will also be looking to replace the New Zealand chief executive, David McLean, who retires tomorrow.
In the meantime, general manager of institutional and business banking Simon Power will act as chief executive.
"Westpac New Zealand continues to have strong support for what it is delivering for customers and its role in the Westpac Group," Power said.