High gas prices, failure of the government to control the federal deficit, and persistently high unemployment has soured the attitude of workers toward investing, a poll released Thursday says.

The poll conducted by Gallup for Wells Fargo & Co. shows investor optimism slid from February to May.

The investor optimism index measured by the poll fell to 33 in May from 42 in February. The index hit its all-time low of negative 64 in February 2009 as the stock market was hitting its bottom.

Prior to the economic downturn, the index was soaring at 95 in May 2007.

The top three factors hurting the investing climate are the price of energy, cited by 79 percent of respondents, the federal budget deficit at 75 percent and the unemployment rate at 67 percent.

The May poll shows optimism among workers fell 31 percent from 35 in February to 24 in May while U.S. retirees maintained a consistent optimism level of 61 in both the February and May polls.

The Wells Fargo/Gallup Index is based on quarterly telephone interviews. The poll was conducted with 1,099 investors aged 18 and older from May 2 through May 10. Of those questioned 64 percent were working and 36 percent were retired. The average age of retirees surveyed is 69 and that of workers is 45.

The significant drop in optimism among workers was startling, said David Carroll, head of Wells Fargo’s wealth, brokerage and retirement business.