An assistant U.S. attorney involved in prosecuting a high-profile terrorism case is suing Attorney General John Ashcroft (search), alleging he and his agents at the Justice Department are retaliating against him for his testimony to the Senate Finance Committee.

Richard Convertino (search) of Detroit also is suing several officials at the Justice Department. The case is being handled by the National Whistleblower Center (search), which has represented FBI agents and other whistleblowers in recent cases involving terrorism.

Raw Data: Convertino v. Dept. of Justice, et al. (pdf)

Justice officials said Tuesday that they will not discuss the case because they do not comment on ongoing litigation and internal probes. Convertino is the subject of a months-long internal investigation at the Justice Department.

Convertino filed the lawsuit Friday in federal court in Washington. He alleges "gross mismanagement" in the war on terrorism. He claims that the Justice Department is upset that he "cooperated" with Sen. Charles Grassley (search), chairman of the Senate Finance Committee.

Last year, Convertino spoke with Grassley's staff and allowed them to interview Youseff Hmimssa (search), a government witness who had testified in a now-controversial terrorism case, U.S. v. Koubriti (search). Convertino also testified before the committee about the Koubriti case.

Convertino alleges that a Justice Department official told him that Grassley is not "our friend" and "hates the FBI." According to Convertino, the officials also said that Grassley was a "problem" since the senator had placed a hold on certain judicial nominees, according to the court papers.

Convertino claims that in retaliation for his cooperation with the Senate panel, an internal investigation was opened against him and information from it was leaked to the media.

On Tuesday, Grassley was careful not to suggest any wrongdoing by the Justice Department while still expressing concern for whistleblowers.

"Whistleblowers put a lot on the line to protect the public," Grassley said. "They deserve strong protections against intimidation, harassment, demotion or even dismissal for doing the right thing."

Convertino also claims that the government has exaggerated results in the war on terrorism; interfered with the Koubriti case; and deliberately divulged the name of one of his confidential informants, putting the informant at "grave risk."

The informant, according to Convertino, was forced to flee the United States, making him unavailable to prosecutors seeking information from him about current and future terrorist activities.

A federal judge in Detroit did admonish Ashcroft for some statements he made to the press during the Koubriti case.

In the trial, the jury found two defendants guilty of document fraud and conspiracy to provide material support for terrorism. One other was found guilty of document fraud but acquitted of terror charges. And the fourth was acquitted on all counts.

Since then, the prosecution has admitted that it failed to turn over evidence during the trial that might have assisted the defense, including a letter from an imprisoned drug gang leader who claims Hmimssa made up his story. The letter was handed over to defense attorneys after the trial ended.

The case, the first major post-Sept. 11 terror prosecution, is now in danger of unraveling. But a lawyer for Convertino said he believes his client made the right decision in not disclosing the letter because it wouldn't have affected the trial's outcome.

According to the suit, Convertino said he first complained to his supervisors more than a year ago about his Washington supervisors' interference in the case and their continuously placing "perception over reality to the serious detriment of the war on terror."

Convertino said he has frequently complained about "the lack of support and cooperation, lack of effective assistance, lack of resources and intradepartmental infighting" in terrorism cases. In his suit, he included an e-mail from another prosecutor in the case that shows Convertino complained that efforts by Justice's terrorism unit in Washington to "insinuate themselves into this trial are nothing more than a self-serving effort to justify the existence" of the unit.

"They have rendered no assistance and, are in my judgment, adversely impacting on both trial prep and trial strategy," the e-mail cited in the lawsuit states.

But one of the court-appointed defense attorneys who faced Convertino said he thinks at least one section of the lawsuit "seems completely unfounded."

Rather than complaining about a lack of resources, Convertino's resources "appeared to us to be completely unlimited," said James Gerometta.

Convertino is seeking damages under the First Amendment (search) and Privacy Act (search). The chief lawyer of the center representing him successfully helped Linda Tripp win damages under the Privacy Act for the leak of information from her Pentagon personnel file after the Monica Lewinsky affair.

Fox News' Anna Stolley and The Associated Press contributed to this report.