Fannie Mae’s chief executive officer, Franklin Raines, may lose his job after the Securities and Exchange Commission ruled that the company violated accounting rules, shareholders said.

Mr. Raines told Congress in October that he would take responsibility if the bookkeeping at the largest source of American mortgage financing was found to be flawed. The chief financial officer, J. Timothy Howard, also testified in defense of the accounting.

“I can’t fathom that Raines and Howard can survive this,” said Michael Mullaney, who owns Fannie Mae stock and bonds among the $10 billion he helps manage at Fiduciary Trust Company in Boston. “Before it was just an accounting issue and now it’s an accounting and credibility issue.”

The Washington-based, governmentchartered company may have to restate earnings by $9 billion after the SEC’s chief accountant, Donald Nicolaisen, said Wednesday that he “advised” Fannie Mae executives that they should fix their derivatives accounting. Derivatives are financial contracts whose val ue is derived from debt, equity securities, currencies, and commodities.

A Fannie Mae spokesman, Chuck Greener, declined to comment on Mr. Raines’s status with the company. Ann Korologos, the Fannie Mae director who is handling the board’s response to findings of accounting errors, didn’t return a phone call requesting a comment.The $9 billion figure was Fannie Mae’s estimate last month. Fannie Mae and Freddie Mac own or guarantee almost half the $7.6 trillion mortgage market.

Mr. Raines has told investors and lawmakers that his company’s accounting was sound in the 18 months since Freddie Mac, Fannie Mae’s smaller rival, disclosed that it understated earnings by $5 billion in order to reduce profit volatility.

Mr. Raines, a 55-year-old former Rhodes scholar, investment banker at Lazard, Freres & Company, and budget director in the Clinton administration, told Congress on October 6 that he only certifies company accounting “after receiving assurances that I can say with confidence that these documents fairly present, in all material respects, the financial condition, results of operations and cash flows of the company.”

Mr. Raines also told the House Financial Services Committee that he considered the SEC the “final authority” on accounting disputes and he would hold himself responsible for any major accounting mistakes.

“If after a thorough review of all the facts it is determined that our company made significant mistakes, our board and our shareholders will hold me accountable and I’ll hold myself accountable,” he said.

The testimony followed a September report by the company’s regulator, the Office of Federal Housing Enterprise Oversight, that accused the company of accounting errors. Ofheo said Mr. Howard “failed in providing adequate oversight.”