Investors are increasingly worried that troubles in the euro zone and China will hurt global economic growth this year, curbing gains in equity and commodity markets, a Barclays Capital survey showed on Monday.

Slower-than-expected growth in the United States and Europe is the largest threat to global equities in the next three months, while a slowdown in China is the biggest challenge to emerging markets, according to the survey, conducted in June among 862 institutional investors.

The European debt crisis is the second-biggest concern for emerging markets, even as nearly 75 percent of the respondents believe Greece will restructure its debt in the next 12 months.

Uncertainty has increased remarkably, with responses to many of the questions evenly distributed among all the alternatives, Barclays' head of emerging markets research Piero Ghezzi and currency strategist Paul Robinson wrote in a report.

It is easy to understand the lack of confidence in growth or very widespread views, given the many risks facing the global economy at present, they said.

This uncertainty is reflected in the amount of risk being taken this quarter: 40 percent of clients are running a light or very light amount of risk relative to capacity, up from 31 percent last quarter.

Only 31 percent of the respondents expect equities to return more than 5 percent in 2011, compared with more than 80 percent in the previous quarter's survey.

On the other hand, more than 20 percent of the investors forecast equities will fall 5 percent or more this year, versus only 7 percent in the previous quarter.

Overall, 20 percent of the respondents said equities will be the best-performing asset class this year.

LOSING THEIR LUSTER: COMMODITIES

Commodities, viewed as the most attractive investment in the previous quarter by 41 percent of the respondents, emerged as the least attractive asset class, with only 15 percent of the votes.

Bonds, which tend to outperform when growth fears increase, were considered the favorite asset class by a little more than 30 percent of the respondents, compared with 20 percent in the previous poll.

Changes in the Federal Reserve's monetary policy were not seen as a short-term concern by most investors.

Among credit investors, more than 70 percent of answers suggested that the end of the Fed's quantitative easing program would have limited impact on credit markets.

Nearly 80 percent of equity investors see no change in the trend until the Fed actually tightens monetary policy, either by raising interest rates or shrinking its balance sheet.

Fiscal issues appeared to be even less of a concern, with fewer than 4 percent of fixed-income investors expecting the Treasury to miss a bond coupon payment.

(Reporting by Walter Brandimarte; Editing by Jan Paschal)

China Barclays