The former Fannie Mae employee who assisted federal regulators in an investigation of the company's accounting will not testify at a congressional hearing next week.

Roger L. Barnes, a manager in the Fannie Mae controller's office, raised concerns about accounting practices at the company, leading to an internal inquiry. His concerns were cited in a report released last week by the Office of Federal Housing Enterprise Oversight, which alleged that improper accounting was pervasive at Fannie Mae as part of an effort to make earnings more predictable. The report said Fannie did not adequately investigate Barnes's complaints, though they "were raised to the highest levels" of the company, including an internal auditor's presentation to the audit committee of the board of directors.

The Securities and Exchange Commission and the Justice Department are investigating the agency's findings.

"We are in touch with [the] Justice Department regarding the Barnes situation and there are a number of legal complexities that prevent him from coming to testify before the subcommittee on Wednesday," said Peggy Peterson, a spokeswoman for the House Financial Services Committee. She declined to elaborate.

Prosecutors frequently seek to coordinate their ongoing criminal investigations with securities regulators and lawmakers, sometimes asking Congress to hold off until they have had a chance to question key witnesses

Fannie told the regulators about Barnes's complaints as they were conducting a special examination of the company's accounting, following an accounting scandal last year at Freddie Mac, another government-chartered mortgage finance company.

The House subcommittee overseeing Fannie and Freddie plans to hear testimony from Fannie Mae chairman and chief executive Franklin D. Raines, vice chairman and chief financial officer J. Timothy Howard, and Ann McLaughlin Korologos, who heads a committee of Fannie's board appointed to address the regulators' allegations.

Barnes will submit written testimony, said his lawyer, Debra S. Katz. Armando Falcon Jr., director of OFHEO, is slated as the first witness.

Peterson said she did not know if the witnesses would testify under oath. "We are perfectly prepared to testify under oath, but that is a procedural choice the committee makes," said Brian Faith, a Fannie Mae spokesman.

The hearing will focus on Fannie Mae's corporate culture, which Rep. Richard H. Baker (R-La.), chairman of the subcommittee, views as "lax and manipulative," said Michael DiResto, a Baker spokesman.