Fuel spending rose nearly 11% in August, partly reflecting the steady increase in petrol prices during the month.
ASB economist Christina Leung estimated petrol prices increased about 6% in August, suggesting there was also an increase in sales volume of petrol.
The seasonally adjusted value of total retail industry transactions on electronic cards rose 3% to $4.27 billion in August, according to Statistics New Zealand. Spending on fuel jumped to $689 million, its biggest monthly increase since the series began a decade ago.
Local retailers have had to contend with softer household demand in recent years, as historically low interest rates and persistently high unemployment encouraged people to repay debt, rather than increase spending.
Statistics NZ said other vehicle-related expenses rose 0.8% to $114 million in August.
That came after figures showed consumer spending in the second quarter was underscored by record expenditure on cars and auto parts.
New Zealand's total core spending on electronic cards, which excludes motor vehicle-related industries, rose 1% to $3.46 billion, boosted by an increase across all industry groups. The largest increase in card spending was on consumables up 0.8%, or $12 million, to $1.52 billion.
Ms Leung said the trend in retail spending had been improving gradually in recent months.
"Encouragingly, the increase in sales was broad-based across all categories."
The figures supported growing consumer confidence in recent months, and was likely to be supported by a rising number of house sales.
"While the substantial increase in retail card spending over August was largely driven by higher spending on fuel ... there are also encouraging signs of an improvement in underlying household spending," she said.
However, the June quarter employment data highlighted the patchiness of the recovery in the labour market and households remained cautious.
"There remains little urgency for the Reserve Bank to raise the official cash rate and we expect it will remain on hold until June 2013."
The total value of electronic card spending, including services and non-retail industries, rose 2.4% to $5.62 billion. Unadjusted spending on electronic cards advanced 6.3% to $5.48 billion in August.
