The Reserve Bank has sold a large amount of New Zealand dollars in its biggest move in the currency markets in over a year.
Information published on the central bank's website shows it sold $200 million for foreign currency in December last year.
Westpac currency strategist Imre Speizer says the last time the bank sold more New Zealand dollars was in 2008 when it was attempting to bring down the value of the currency.
Mr Speizer says the Reserve Bank is unlikely to be trying to repeat that strategy.
"That was publicised ... and explicitly designed then to push down the Kiwi dollar. You can't say that about this particular month of intervention - certainly, the amount's too small."
However, Mr Speizer says the Reserve Bank may be shifting to a more active management of its foreign currency reserves where it sees the chance for financial gain similar to the approach taken by the Reserve Bank of Australia.