Spending by wage-earning households fell a real 3.3 percent in July from a year earlier to 323,515 yen, for the first decline in two months, the government said Tuesday.
The result compared with the average market projection of a 0.9 percent expansion, fueling concern that personal consumption may slow in the July-September quarter after posting sharp increases in the first half of 2005.
The average monthly income of salaried workers' households came to 572,399 yen, down 3.6 percent in real terms from a year before, the Internal Affairs and Communications Ministry said in a preliminary report.
Real figures are adjusted for inflation.
Disposable income shrank a real 3.3 percent to 480,128 yen.
A ministry official said the weaker than expected data show the government "cannot be optimistic" over a domestic demand-led recovery.
The government and the Bank of Japan said earlier the country has emerged from an economic lull.
Spending on transportation and communications, including vehicle purchases, fell 11.9 percent in real terms in July from a year earlier to 43,088 yen, according to the report.
Spending on education, including school tuition, was down a real 14.4 percent to 13,605 yen.
Outlays for furniture and housing equipment dropped 6.0 percent to 12,267 yen.
Spending on food, the biggest component, fell a real 0.1 percent to 72,275 yen.
In contrast, spending on housing, including maintenance and repair costs, increased a real 9.1 percent to 21,241 yen.