"Your pension-fund manager may be using your retirement money to drive up the price of oil," said Rep. Bart Stupak, D-Mich., at a hearing earlier this week on speculation in commodities.

"What would happen if pension-fund managers decided to increase their commodity investment by another 20-fold?" he asked.

Speculators put money into commodity markets simply to make money on their investments — unlike commercial investors, who are actually buying or selling orders for physical goods.

Energy analysts say it's unclear what effect speculators have had on oil prices, which climbed briefly to a new record above $142 on Friday before falling back.

But Stupak and other lawmakers have already dashed off more than a dozen proposals to rein in commodity trading, including limiting how many contracts speculators can hold and closing loopholes that allow them to skirt regulations.

Sen. Joe Lieberman, I-Conn., proposed banning pension funds and other large investors from commodities altogether. He dropped the idea after vigorous opposition by an association of public and private pension funds.

Schlachter, who is also managing director for investment-consulting firm Wilshire Associates, called the idea "horrendously bad." He said pension funds should not be compared to Wall Street speculators, who assume huge risks every day to maximize returns.

"The pension plans we work with are using commodities only as a long-term hedge against inflation," he said.

Unlike the stock market, where there are a limited number of shares for each company, futures markets have no limits on contracts available. As long as a buyer can find a seller for each contract, investment opportunities are virtually unlimited.

Critics say retirement funds that accumulate contracts are artificially driving up commodity prices. In the case of oil, that means higher gas prices and more expensive food and other goods.

"If they're going to be in the futures market, they need to trade rather than take this buy and hold strategy," said Michael Masters, portfolio manager of hedge fund Masters Capital Management. "That is the worst possible thing for the futures market."

Masters and other experts told members of Congress this week that eliminating excessive speculation could drive oil prices down to about $65 a barrel, less than half the current price.