WASHINGTON — Americans' retirement plans have lost as much as $2 trillion in the past 15 months — about 20 percent of their value — Congress' top budget analyst estimated Tuesday as lawmakers began investigating how turmoil in the financial industry is whittling away workers' nest eggs.

The upheaval that has engulfed financial firms and sent the stock market plummeting is also devastating people's savings, forcing families to hold off on major purchases and even delay retirement, Peter Orszag, the head of the Congressional Budget Office, told the House Education and Labor Committee.

"Unlike Wall Street executives, America's families don't have a golden parachute to fall back on," said Rep. George Miller, D-Calif., the panel chairman. "It's clear that their retirement security may be one of the greatest casualties of this financial crisis."

More than half the people surveyed in an Associated Press-GfK poll taken Sept. 27-30 said they worry they will have to work longer because the value of their retirement savings has declined.

Orszag indicated the fear is well-founded. Public and private pension funds and employees' private retirement savings accounts — like 401(k)s — lost about 10 percent between the middle of 2007 and the middle of this year, and lost another 10 percent just in the past three months, he estimated.

Private retirement plans may have suffered slightly more because those holdings are more heavily skewed toward stocks, Orszag added.

"Some people will delay their retirement. In particular, those on the verge of retirement may decide they can no longer afford to retire and will continue working," Orszag said.

A new AARP study found that because of the economic downturn, 1 in 5 workers 45 and older has stopped putting money into a 401(k), IRA or other retirement savings account during the past year, and nearly 1 in 4 has increased the number of hours he works. More than one-third of these workers have considered delaying retirement, according to the study, which also found that more than half now find it difficult to pay for basic items such as food, gas and medicine.

The hearing came just as workers are receiving — or about to receive — their quarterly retirement savings account statements, which are likely to show disheartening drops in the value of holdings.

Jerry Bramlett, the head of BenefitStreet Inc., a retirement savings plan administration company, said there's a risk that people will overreact to the bad news by pulling their money out of the accounts, which could add to their potential losses.