General Motors Corp. (GM) shares fell 3 percent Wednesday and a major credit agency said it was reviewing whether to cut GM's debt ratings further after the world's biggest automaker offered an even starker picture of its numerous financial perils.

In an annual regulatory report filed after the market closed Tuesday, GM restated financial results from 2000 through 2004 because of a litany of accounting errors. GM had said March 16 that it was delaying filing its annual report because of an internal investigation into those errors.

GM also said it is restating financial results for its financing arm, General Motors Acceptance Corp., from 2003 through the third quarter of 2005. The restatement relates to the improper classification and presentation of cash flows for certain mortgage loans.

In addition, GM said it was uncertain that it could complete the sale of a majority stake in GMAC as it had hoped.

By Wednesday afternoon, GM shares lost 69 cents to $22.06 on the New York Stock Exchange.

The long-anticipated sale of a 51 percent GMAC stake was seen as a way to separate the division's debt rating from GM's own junk rating and raise as much as $15 billion in badly needed cash for the struggling automaker.

"We are uncertain at this time if any transaction with respect to GMAC ... will occur or, if any transaction were to occur, on what terms," GM said. GM added that even if a transaction is completed, it's possible GMAC's credit rating could still hinge on GM's.

GM had hoped a new parent for GMAC would bring investment-grade credit ratings to the finance business, which was slashed to junk status last year alongside its sliding automotive parent. It was those ratings that caused GM to consider the planned sale, which was announced in October.

Standard & Poor's Ratings Services said Wednesday that it was reviewing whether to lower GM's debt ratings further. Its long-term corporate credit rating is currently a B, which is five notches below investment-grade status. S&P said ratings of GMAC won't be affected.

GM said it had concluded an internal investigation into Residential Capital Corp., GMAC's mortgage subsidiary, and determined that cash flow relating to certain mortgage activities was inappropriately classified.

The changes reduced operating cash flows but increased investing cash flows between 2002 and the first three quarters of 2005, the automaker said. GM said the restatement doesn't affect the income statements or net cash flows of GM, GMAC or ResCap.

GM also said it began investigating errors in the way it booked credits from suppliers, including Delphi, last April after getting a subpoena from the Securities and Exchange Commission. The SEC, which was seeking information on retroactive price adjustments GM had received from Delphi, is continuing to investigate GM and its suppliers.

In Tuesday's filing, GM said a federal grand jury recently issued a subpoena in connection with supplier credits. And it said the SEC recently issued a subpoena in connection with an investigation of transactions in precious metal raw materials used in GM's auto manufacturing operations.

GM said it erroneously booked supplier credits as a reduction of cost to sales between 2000 and 2004. After restatement, a deferred credit of approximately $548 million existed as of December 2004, which will be recognized as a cost of sales in future periods, the automaker said.

Burnham Securities analyst David Healy said GM's restatements were largely housekeeping measures that will have no effect on GM or GMAC's cash flow.

"If it wasn't GM in crisis mode and the whole feeding frenzy going on in the media, a small restatement like this wouldn't get any attention," Healy said.

But Healy said it was important for GM to get its finances straightened out in preparation for the possible GMAC sale. The filing "removes a minor burden" to the sale, Healy said.

Credit ratings agencies have said that they would probably lower GMAC's ratings closer to those of GM if the stake in the finance division isn't sold. Those lower ratings would dramatically raise the cost of funding for GMAC, as well as severely impede its access to capital.

If no sale occurs, GM said, "GMAC's access to capital may be seriously constrained, as most unsecured funding sources may decline, including bank funding."

The cost of secured funding may also rise without the sale.

A higher cost of funding would "significantly lower earnings and dividends," the filing said. "GMAC may need to consider divesting certain businesses in order to maintain adequate liquidity," the filing continued.

GM lost $10.6 billion in 2005, largely due to declining U.S. sales and rising benefits costs. The company is in the midst of a restructuring plan and on Tuesday announced it was laying off several hundred salaried workers. GM also has offered buyouts to all of its 113,000 U.S. hourly workers in the hopes of cutting its hourly work force by 30,000 by 2008.