Mr. Yukawa, who now works at PartnerRe Asset Management, a money management firm in Greenwich, Conn., did not return requests for comment.

Goldman has said it will fight the accusations from the S.E.C., which claims Goldman built the Abacus investment to fall apart so a hedge fund manager, John A. Paulson, could bet against it. And in response to this article, Goldman said it did not improperly influence the ratings process.

Chris Atkins, a spokesman for Standard & Poor’s, noted that the agency was not named in the S.E.C.’s complaint. “S.& P. has a long tradition of analytical excellence and integrity,” Mr. Atkins said. “We have also learned some important lessons from the recent crisis and have made a number of significant enhancements to increase the transparency, governance and quality of our ratings.”

David Weinfurter, a spokesman for Fitch, said via e-mail that rating agencies had once been criticized as opaque, and that Fitch responded by making its models public. He stressed that ratings were ultimately assigned by a committee, not the models.

Officials at Moody’s did not respond to requests for comment.

The role of the rating agencies in the crisis came under sharp scrutiny Friday from the Senate’s Permanent Subcommittee on Investigations. Members grilled representatives from Moody’s and Standard & Poor’s about how they rated risky securities. The changes to financial regulation being debated in Washington would put the agencies under increased supervision by the S.E.C.

Carl M. Levin, the Michigan Democrat who heads the Senate panel, said in a statement: “A conveyor belt of high-risk securities, backed by toxic mortgages, got AAA ratings that turned out not to be worth the paper they were printed on.”

As part of its inquiry, the panel made public 581 pages of e-mail messages and other documents suggesting that executives and analysts at rating agencies embraced new business from Wall Street, even though they recognized they couldn’t properly analyze all of the banks’ products.