WASHINGTON - The Senate Commerce Committee voted unanimously yesterday to subpoena Kenneth Lay, the former Enron chairman who refused to answer questions voluntarily about the collapse of the energy trading company.

"We have no choice," said Sen. Byron Dorgan, D-N.D.

The vote came as another Senate committee was hearing from former Enron employees whose retirement savings were depleted when the firm's stock dropped from roughly $80 a share to less than $1.

One, Deborah Perrotta, wept several times while she described the loss of about $40,000.

"This isn't right," she said. "We put all our ingenuity and creativity at the service of the company we believed in and trusted and were certain would reward our commitment."

Now, she said, she can't afford the family's $300 monthly prescription drug bill or to pay for her daughter's wedding in September.

Officials said the subpoena would command Lay to appear Feb. 12 - but there was little expectation that he would provide answers to the questions lawmakers seemed eager to ask.

Lay also was ordered to appear before a House panel investigating Enron, on Feb. 14.

"I'll bet you a dollar to a doughnut that he doesn't testify and invokes his right under the Fifth Amendment," said Sen. John Breaux, D-La. The amendment guarantees protection against self-incrimination.

Kelly Kimberly, a spokeswoman for Lay, said the subpoena had been expected and "we anticipate that they will be in touch with Mr. Lay's attorney to work out the details." She said Lay's attorney also is working with the House subcommittee seeking Lay's testimony.

The Senate committee action was the latest development in what has taken on the appearance of a congressional cottage industry - a dozen committees and subcommittees probing various aspects of the biggest bankruptcy in the nation's history.

Millions of investors lost money - and thousands of current and former Enron employees lost the great bulk of their retirement savings when the company collapsed. An internal investigation blamed senior management for failing to provide proper oversight into a complex web of partnerships that helped the company hide debt and report unrealistic profit figures.

The taint has spread beyond the Houston-based company, and the head of the accounting firm Arthur Andersen appeared at a separate congressional hearing to defend its work with Enron.

"I did not do the audit of the company," Joseph Berardino, the Andersen chief, said at one point. "Information was withheld from us."

He said Enron did not provide critical information about one of the partnership's arrangements with Barclays Bank of Britain. He said that if the auditors had been given that information in 1997, Andersen would have objected to Enron's accounting for the partnership.

Later, he said, "At the end of the day we do not cause companies to fail."

His testimony drew scorn from lawmakers in both parties. "You have squandered the integrity of your company," said Rep. Gary Ackerman, D-N.Y.

The vote in the Senate committee came little more than 24 hours after Lay was to have appeared. He canceled his testimony on short notice after his lawyer said the proceedings had taken on a prosecutorial tone.

Some senators expressed skepticism of claims by Lay that he did not know details about the financial dealings that an internal Enron investigation called "a systematic and pervasive" attempt by senior managers to "misrepresent the company's financial condition" by hiding millions of dollars in debt and losses.

If he didn't know, said Sen. Peter Fitzgerald, R-Ill., "we have to conclude that Kenneth Lay was perhaps the most out-to-lunch CEO in America."

To underscore the bipartisan determination to investigate, the formal proposal for the subpoena was advanced by Sen. Ted Stevens of Alaska, second-ranking Republican on the Democratic-controlled committee.

While the committee vote was unanimous, there was some partisan sparring about an allegation from Sen. Ernest Hollings, D-S.C., the chairman, that the Bush administration and Enron had participated in a "cash and carry" relationship.

"I am concerned about the political rhetoric that has occurred," said Sen. Kay Bailey Hutchison, R-Texas. "I just hope that we are going to use this committee to gather information and not to ventilate on political issues that really have no place here."

Hollings said the Enron debacle should provide Congress with the impetus to pass legislation reducing the role of money in political campaigns.

The Justice Department and the Securities and Exchange Commission also are investigating the collapse of Houston-based Enron, and President Bush has called for an overhaul of laws designed to protect retirement savings plans known as 401(k)s.

Hollings has called for a special prosecutor should investigate Enron.

The Justice Department said in a statement that it sees no reason to appoint a special counsel to investigate Enron. "No person involved in pursuing this investigation has any conflict, or any ties that would require a recusal," the department said.

Lay resigned Monday from Enron's board after relinquishing his position as Enron chairman on Jan. 23. Enron and Lay have been among Bush's largest campaign contributors.

Opening a week of Enron hearings, William Powers, the head of the internal Enron investigation, said Monday that senior Enron executives involved in the partnerships "enriched themselves ... by tens of millions of dollars that they should never have received."