New Zealand's payments position with the rest of the world worsened by about $500 million in the last quarter.
The balance of payments measures the value of New Zealand's international dealings, including goods, services and the transfer of investment income.
Statistics New Zealand says high prices for petrol and petrol products boosted the current account deficit for the year to the end of September to $15.5 billion.
The deficit is equal to 8.6% of the economy, up from 8.4% at the end of the June quarter, and one of the highest in the developed world.
Radio New Zealand's economics correspondent says foreign investors could abandon New Zealand if the deficit gets too high, putting downward pressure on the dollar and increasing the cost of overseas' borrowings.
But economists say New Zealand has run higher deficits in the past and foreign investors show no sign - yet - of passing over the country for other destinations.
ASB chief economist Nick Tuffley says the current account deficit still compares favourably to 2006 when it was about 9.3% of GDP. Mr Tuffley expects it will get close to 9% early next year before declining.
But BNZ economist Craig Ebert believes the deficit could account for as much as 10% of the economy next year as commodity markets continue falling next year.
New Zealand is already in recession. Latest Gross Domestic Product figures are due to be issued on Tuesday. They are expected to show the economy has contracted for a third successive quarter.
