Consumer confidence has slumped as the slowing housing market and rising fuel prices potentially start to bite.

The Westpac McDermott Miller Consumer Confidence Index fell 5.1 points in September, taking it to a level of 103.5 - the lowest level for the Index since September 2012.

"New Zealand households are particularly concerned about the outlook for their own finances and the general economy over the next year," said Westpac chief economist Dominick Stephens.

"Expectations for their own circumstances in the year ahead are at their lowest, outside of an actual recession, in the history of the survey."

It wasn't clear whether consumers were starting to feel the real impact of the slowdown or 
whether they were worried by what they were hearing about business confidence, he said.

"The groups that benefited from the Government's Families Package, which took effect from 1 July, did report some improvement in their own circumstances," Stephens said.

"But this appears to have been outweighed by other concerns in most consumers' minds.

"But beyond the initial boost from the Families Package, all age groups expected a decline in their own circumstances, and in the wider economy, over the coming year."

A fall in the confidence of Aucklanders pointed to two likely causes for the dip, he said.

"The slowdown in the housing market and rising fuel prices are potential factors behind the drop in confidence.

"These factors were being most acutely felt in the Auckland region, which saw a particularly sharp drop in confidence."

The confidence dip comes as actual spending data for August remained strong.

Seasonally adjusted total retail spending on credit and debit cards rose 1 per cent after lifting 0.2 per cent in July, according to Stats NZ.

Core retail spending, which excludes vehicle-related industries, rose 0.7 per cent, after increasing 0.3 per cent in July.

The card data showed spending rose in all of the six retail industries in August.

The Westpac McDermott Miller Consumer Confidence Index summarises the net balance of optimistic/pessimistic responses to five questions: how households' financial
situation has changed over the past year; whether now is a good time to buy a major household item; how households expect their financial situation to change over the coming year; and near-term and longer-term prospects for the New Zealand economy as a whole.

The survey was conducted over September 1-10, with a sample size of 1556. An index number over 100 indicates that optimists outnumber pessimists. The margin of error of the survey is 2.5 per cent.