"The value-adding, which occurs offshore prior to arriving in New Zealand, contributes to the increases in the total import value."
Petroleum and products imports rose $795m (206 percent) to $1.2b in June on the same month a year ago after the closure of the refinery.
The rise in volumes and prices reflected the rebound from last year's Covid-19 restrictions which had dampened demand, as well the rise in global prices.
Stats NZ said the average value for each unit of imported fuel rose 133 percent for diesel and 125 percent for petrol.
Rises in the import of machinery and equipment also drove up the monthly import bill of $7.1b, up 25 percent on a year ago.
Meat and dairy continued to dominate exports, which lifted 7.7 percent to $6.4b.