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Illinois Rep. Jesse Jackson Jr.'s revelation that he has been an informant for U.S. Attorney Patrick Fitzgerald has thrust the famed federal prosecutor back into the spotlight amid questions about whether he crossed the line in his pursuit of Gov. Rod Blagojevich.

Fitzgerald sent shock waves through the nation last week with his arrest of Blagojevich on federal corruption and bribery charges, including the jaw-dropping allegation that the governor had slapped a price tag on President-elect Barack Obama's vacant Senate seat.

Jackson was identified as one of the candidates Blagojevich was considering for the Senate seat, and the criminal complaint said his supporters were willing to raise $1.5 million for the governor if he picked the congressman.

But Jackson's spokesman revealed Tuesday that the Illinois congressman "has shared information with federal prosecutors about public corruption during the past several years, including information about Blagojevich and others."

Lawyers interviewed by FOXNews.com, including former U.S. attorneys, said nothing is inappropriate about a congressman helping a federal prosecutor root out corruption.

"It shouldn't raise eyebrows," former Attorney General Janet Reno told FOXNews.com, adding that "it is not bad to inform on someone in certain situations."

Michael McKay, who served as a U.S. attorney under former President George H.W. Bush, agreed.

"In fact, elected officials have a citizen's responsibility like everyone else to alert the authorities of wrongdoing," he said.

But Fitzgerald's comments about the criminal complaint at the news conference he held to announce Blagojevich's arrest have raised some eyebrows and drawn charges of their own.

"It's unethical, plain and simple," said Victoria Toensing, a Washington lawyer and former deputy U.S. attorney.

At the news conference, Fitzgerald said he publicized the charges against Blagojevich before going for an indictment because "we were in the middle of a corruption crime spree and we wanted to stop it."

He called the charges against Blagojevich "a truly new low," adding that the "conduct would make Lincoln roll over in his grave"

"The prosecutor is not supposed to talk outside the four corners of the indictment," Toensing said. "You can talk about the facts in the complaint. But you're not supposed to talk about your reaction to it, law enforcement's reaction to it."

Toensing predicted Fitzgerald's comments will prompt Blagojevich's defense attorney, Ed Genson, to file a motion to dismiss the case against him.

"Prosecutors are supposed to be fair," she said. "He can hit hard blows but not foul ones."

But whether a motion to dismiss succeeds will depend on who the judge is, Toensing said.

McKay said he was "mildly troubled" by Fitzgerald's comments.

"When I was a U.S. attorney, it was my practice to base my initial comments on the complaint," he said. When he took questions from reporters, "my answers would be drawn from what was in the complaint."

McKay added that Fitzgerald's comments aren't an issue of ethics but rather of style, describing the Lincoln reference as "artistic."

"I don't find it particularly troubling," he said. "It's just something I didn't do."

Peter Vaira, another former U.S. attorney, said Fitzgerald had to make the comments to explain why he brought charges without getting an indictment.

"He had to grind it to a halt and let the [Illinois] Legislature clean it up," he said. But he added that the Lincoln reference "might have been over the top."

"He could have been more cautious," Vaira said.