The Westpac-Melbourne Institute consumer sentiment index fell by 2.2 per cent in January to 89.9 points, down from December's 92 points.
On an annual basis, consumer sentiment has fallen 12.8 per cent.
Westpac senior economist Matthew Hassan said that after a recovery in December, consumer sentiment fell again in January as the government's $10.4 billion fiscal stimulus failed to keep consumers upbeat.
"The initial boost from aggressive rate cuts and fiscal bonus payments may be starting to wane,'' he said.
The survey's 1200 respondents were polled in mid-January in a month when the Reserve Bank of Australia does not meet, and after parents, pensioners and carers were given pre-Christmas handouts.
With news about the global financial crisis dominating the headlines, Mr Hassan said consumers were wary.
"The survey detail tells the real story: consumers are entering 2009 with great trepidation,'' he said.
"Whereas the last few months have seen sustained improvements in responses to questions on family finances, 'time to buy a major household item' and the economic outlook for the next five years, consumers have become increasingly pessimistic about the outlook for the year ahead."
The measure asking consumers about economic conditions in the next 12 months fell by 18.4 per cent in January.
The question about whether now was a good time to buy a major household item declined 3.5 per cent in the month.
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