Investor confidence in the economy deteriorated in August to its lowest level in a year, as the growing housing turmoil compounded worries over high energy prices, a survey showed on Monday.

The UBS/Gallup Index of Investor Optimism fell for a third straight month to 73 in August, down 14 points from 87 in July.

Almost two-thirds of the investors polled believe the United States in now either in a slowdown or a recession, up from 55 percent in July and the highest since October 2005.

The high-profile troubles in the real estate market, particularly the subprime (mortgage) sector, coupled with ongoing energy price concerns are fueling investor skepticism about the U.S. economy, Mike Ryan, head of UBS Wealth Management Research, Americas, said in a statement.

The financial markets have been on a roller coaster in August on fears about losses in the subprime sector hurting the rest of the economy. From August 1-15, when the survey was conducted, the benchmark Standard & Poor's 500 stock index lost 3.3 percent.

UBS/Gallup said housing and real estate problems now rank second to energy costs in hurting the investment climate a lot. Fifty-four percent of investors cited this as a concern in August, the highest level about housing since the two firms began tracking this issue in October 2005. In July, 41 percent of investors felt this way.

Moreover, Ryan said, signs of an emerging consumer credit squeeze and rising fears of a recession are weighing heavily on investor sentiment.

The survey's gauge on economic dimension, an index on investors' feelings about the direction of the overall U.S. economy, shed 11 points to 5 in August, its lowest since August 2006 when it was at minus 1.

On the other hand, investors' confidence about their individual investments deteriorated less, as the survey's personal dimension reading slipped by 3 points to 69.

The latest survey derived from 804 randomly selected investors, who is a head of household or a spouse in any household with total savings and investment of $10,000 or more. The sampling error in the results is plus or minus 4 percentage points.