In blunt, private letters, the Senate Finance Committee chairman has told Attorney General John Ashcroft (search) he believes the Justice Department has retaliated against prosecutors in a Detroit terror trial because they cooperated with Congress.

Sen. Charles Grassley (search), R-Iowa, has written Ashcroft or his deputies at least three times to accuse department officials of taking "hostile actions" and "reprisals" against the trial prosecutors.

In one letter, Grassley demanded that Assistant U.S. Attorney Richard Convertino (search) and his colleagues in Detroit "be made whole and not suffer reprisals." The senator asked Ashcroft to rectify the matter before it begins "exposing the department to public criticisms."

Grassley also dismissed as "bureaucratic, legalistic spin" the department's explanations for why the prosecution team was subjected to internal investigation.

"Federal law provides individuals who are congressional witnesses or assisting congressional investigations protection from retaliation," Grassley wrote.

Justice officials declined comment.

Convertino, a 14-year career prosecutor, helped win the convictions of three men accused of operating a terror cell in Detroit last summer, but he came under investigation when his bosses learned Grassley's committee had subpoenaed him to testify, said Bill Sullivan, Convertino's attorney.

Sullivan said Convertino had been asked by Grassley's committee last fall to narrowly testify about terror financing schemes, and had no intention of discussing the friction with Washington or the missed evidence opportunities that arose during the trial.

Convertino remains employed by Justice but has been detailed to Congress to assist Grassley. He recently sued Ashcroft, accusing Justice officials of interfering with the case and retaliating against him.

"The complaints that Rick has must be appropriately answered so that no other prosecutors ever be faced with the obstacles that were imposed in the Detroit case," Sullivan said.