Struggling under a cascade of bankruptcy filings in the airline and steel industries, the government's pension insurance agency said yesterday that its deficit has more than doubled in the past year -- to $23.3 billion.

The figure is so large that an overhaul of the way traditional pensions are funded and insured has become essential, several experts said. Pensions of about 44 million workers and retirees are insured by the Pension Benefit Guaranty Corp. If it cannot meet its obligations, taxpayers could be called on to pay the bill, they said.

"The bottom line seems to be that there really is a PBGC crisis, though to date neither Congress nor the [Bush] administration has been treating it as such," said Dallas L. Salisbury, who heads the Employer Benefit Research Institute in the District.

After running a surplus that peaked at $9.7 billion in 2000, the PBGC sank into deficit as the stock market and interest rates used in figuring future liabilities declined. It showed a deficit of $3.6 billion in fiscal 2002. That leaped to $11.2 billion for fiscal 2003.

The agency's deficit or surplus is the difference between the value of its assets and that of the future benefits it promises to cover. Set up under the 1974 Employee Retirement Income Security Act, the PBGC takes over traditional pension plans when the employers that operate them cannot meet their obligations, and it pays the pensions, up to certain limits.

Agency officials hastened to assure workers and retirees that it will be able to continue paying benefits "for a number of years." But, PBGC Executive Director Bradley D. Belt said in a statement, "it is imperative that Congress act expeditiously so that the problem doesn't spiral out of control."

Congress last year approved a bill that called for lawmakers to come up with a comprehensive pension reform plan within two years. Yesterday, Rep. John A. Boehner (R-Ohio), chairman of the House Committee on Education and the Workforce, said in a statement, "We're making progress in putting together comprehensive pension legislation and remain committed to addressing the significant underfunding problems that are putting worker and retiree benefits at risk."

The PBGC put its current liabilities at $62.3 billion, against assets of $39 billion, in its single-employer plan. Its much smaller multi-employer plan, which covers workers mostly in trucking and construction, has liabilities of about $1.3 billion and assets of about $1.1 billion.

The liability figures include pensions that have not yet been taken over by the agency but are likely to be. Most of the growth was in that category, and though the agency does not name companies whose plans it has not yet taken over, $6.4 billion from UAL Corp.'s United Airlines and $2.2 billion from US Airways Group Inc. machinists and flight attendants are almost certainly included.

Those two plans, along with $3.6 billion from dissolved Bethlehem Steel Corp., whose pensions the agency took over last year, would account for about half of the deficit.

The PBGC reported paying $3 billion of pension payments in fiscal 2004, up from $2.5 billion the year before, $1.5 billion in 2002 and $1 billion the year before that. It reported receipts this year of about $1.5 billion in insurance premiums from plan sponsors and an additional $3.3 billion in investment income.

Retiree benefit payments "should skyrocket over the next couple of years as pension payments actually start on recent claims and on UAL and US Airways, when they come in," said Douglas J. Elliott, president of the Center on Federal Financial Institutions, a research group.

Elliott, who has studied PBGC's situation, projects that absent reform the agency will run out of money about 2021.

There are only three places to get the money, Elliott said: the taxpayers, the employers or the stock market.

The market could come to the rescue, but only if "you make a really risky bet and get really lucky," he said. Otherwise, some combination of higher insurance premiums from employers, tighter rules so companies keep their plans' assets up to their liabilities, and perhaps taxpayer assistance seems likely, he said. "There's a lot of pain to be felt here."

Elliott said one idea would be raising special premiums on companies whose plans are underfunded. Such premiums exist but are paid on only about 10 percent of the total underfunding, he said.

"As the deficit keeps growing, you've got healthy employers who don't want to be stuck with higher premiums," said Ken Steiner, of benefits consultant Watson Wyatt Worldwide. "The alternative is to look at unhealthy employers, who are the real risk at the PBGC, but you run the risk of driving them out of business."

And the Employer Benefit Research Institute's Salisbury pointed to another peril that does not appear in the PBGC's balance sheet: the effect if courts disallow so-called cash-balance pension plans.

Last year, the cash-balance plan at International Business Machines Corp. was found by a federal judge to violate federal age-discrimination laws. If that ruling is upheld and Congress does nothing, Salisbury said, operators of those plans may well start terminating them.

"PBGC's most recent data showed that 25 percent of premiums being paid are in cash-balance plans. A meltdown in the cash-balance area would be even more disastrous than other threats they are facing because it would be loss of a huge amount of premium revenue from essentially well-funded plans," Salisbury said.