Fitch ratings agency lowered New Zealand's credit rating by one notch to "AA" on Thursday and expressed concern over its high external debt.
"New Zealand's high level of net external debt is an outlier among rated peers -- a key vulnerability that is likely to persist as the current account deficit is projected to widen again," said Andrew Colquhoun, Fitch's Head of Asia-Pacific Sovereigns.
The country's net external debt hit 70 percent of annual gross domestic product (GDP) in June.
Fitch said New Zealand's current account deficit, which reflects a structural imbalance between savings and investment, is set to climb to 4.9 percent of GDP next year and 5.5 percent in 2013.
Fitch also downgraded by one notch New Zealand's local currency rating from the top "AAA" rating to "AA+".
It noted that New Zealand had one of the highest levels of household indebtedness among developed countries at 150 percent of disposable revenue, which hasn't declined significantly since 2008.
"Nonetheless, New Zealand remains well placed among the world's highly rated sovereign credits, with its creditworthiness supported by moderate public indebtedness, fiscal prudence, and strong public institutions," said Fitch