New Zealand Post says Kiwibank does not have a risky lending portfolio and it's disappointed credit ratings agency Standard and Poor's has amended its outlook to negative.
Standard and Poor's affirmed the credit rating for the postal operator and its subsidiary Kiwibank as A+/A-1, but revised the outlook on the long-term ratings for both entities from stable to negative.
The agency says the outlook reflects a one-in-three chance the rating of New Zealand Post could be lowered in the next two years due to rising economic risks which could affect the credit standing of Kiwibank.
The agency says the bank represents about 70% of the group's consolidated earnings and is a significant contingent liability for the group.
NZ Post guarantees Kiwibank's deposits, which the agency says stood at $12.3 billion at the end of 2012, and borrowings, which were $1.5 billion.
NZ Post Group chief financial officer Mark Yeoman says Kiwibank does not have a lending portfolio which could be perceived as risky.
As at December 2012 it had 3% of mortgages where it was lending 90% and above of a property's value, while other banks have about 8% of that class of mortage, he says.
Mr Yeoman says the long-term outlook rating reflects Standard and Poor's view on broader economic factors rather than anything specific in relation to New Zealand Post or Kiwibank.
"We've established a pretty strong track record with Standard and Poor's in managing our business to the satisfaction of their methodologies."
He says the agency last week reaffirmed NZ Post's current rating as stable, while putting other banks on negative outlook.
Standard and Poor's last week sounded a warning about eight of the country's smaller lenders, saying the increasing risk of a housing boom and persistent current account deficits could damage their creditworthiness.
Kiwibank has high proportion of home lending
The director of Massey University's Centre for Banking Studies, David Tripe, says Kiwibank has a high proportion of home lending, so it will have more loan loss to worry about should things change.
Mr Tripe says the potential impact of changes in the housing market applies to all banks.
NZ Post has approached the Government in the past for capital to help Kiwibank meet stronger capital adequacy requirements, and most recently to ensure the bank continues to grow.