Business confidence among workers with jobs sensitive to economic trends worsened in September for the second month, sending a closely watched index below the key threshold for the first time in eight months, the government said Friday.

The diffusion index of economic confidence among so-called economy watchers on the current state of Japan's economy fell 3.4 points from August to 47.3, the Cabinet Office said in a monthly survey, signaling that the nation's economic recovery may have lost steam as the figure slid below 50.

The office attributed the fall to record-high crude oil prices and the unusually hot summer, which made consumers reluctant to snap up fall clothes. The index is based on whether respondents see economic conditions as improving or worsening in comparison to three months before. A reading of 50 shows that respondents, which include taxi and truck drivers, generally believe economic conditions are flat.