SPRINGFIELD, Ill. -- Attorney General Lisa Madigan has enlisted state help to probe whether Illinois' electric utilities colluded with credit raters to help them raise prices.

On Wednesday, Madigan asked the Illinois Commerce Commission (ICC) to force Ameren Corp. and Exelon Corp. to hand over all correspondence between them and leading credit-rating agencies from the past two years.

Moody's Investors Services recently dropped Ameren's credit rating to "junk" status while Standard & Poor's (S&P's) has warned of similar action. Downgrading credit penalises a company by making debt service and debt issuance more costly.

Madigan has been probing recent consumer price spikes for electricity by subsidiaries of the two parent companies for several weeks. Ameren Illinois serves the downstate Illinois market while Exelon's Commonwealth Edison (ComEd) serves the Chicago area.

Madigan now is checking out a possible connection between power price spikes and credit-rating downgrades. She suspects credit-raters might be doctoring their reports on utilities with a forthcoming rate-rise hearing to increase their chances of landing an increase.

In her filing to the ICC, Madigan noted several cases last year when S&P and Moody's, "issued warnings and downgrades seemingly right on cue to promote the interests of the [Illinois] utilities and their parent companies."

She claims in the filing to have documented three such occurrences in the past month and seven in an 8-day period last fall, the New York Times reported.

The timing and nature of such reports, Madigan's filing added, "have raised troubling questions as to whether the credit rating agencies are providing objective information or promoting the interests of their clients."

The three rating agencies have not yet responded to Madigan's claims. But ComEd CEO Barry Mitchell described as "ludicrous" the notion that credit agencies would let their reports be altered to produce a favorable outcome.

"People who know the financial markets know that's not how those agencies work," the Chicago Daily Herald quoted Mitchell as saying. "Their credibility and their standing in the financial community would be in jeopardy if they did that."

Allegations that large utilities can alter credit-rating agencies first gained steam last year in Oregon, when Portland General Electric was alleged to have 48 changes to an S&P report.