Lawyers for Sen. Ted Stevens (R-Alaska) told a federal judge Friday that a key witness in the criminal case against the Senator has recanted part of his testimony.

The defense is requesting a hearing on the witness’ allegations that the prosecution encouraged him to lie and improperly gave him access to evidence in preparation for his testimony against Stevens.

Stevens was convicted Oct. 27 on seven counts of failing to disclose gifts on his annual financial disclosure forms. The central focus of the case was hundreds of thousands of dollars worth of renovations to his home that were provided by employees of VECO, an oil-services company owned by his friend Bill Allen.

One of the government’s key witnesses was VECO employee Dave Anderson, who testified about the extensive work that he did on the Stevens’ home renovation project while on VECO’s payroll.

In March, Anderson, apparently believing that Allen was planning to have him killed, signed an affidavit saying the government had promised complete immunity for him, his family and his friends in exchange for his testimony against Stevens.

During his trial testimony, Anderson admitted that the affidavit was false, saying there was no promise of immunity.

But in a November 15 letter to the judge, Anderson wrote “I testified to the fact that there was never immunity for me or my family and friends. That simply is not true.” Anderson wrote that he testified that the affidavit was false only because he thought it would ensure that it would end his involvement in the case; if he had not believed there was an immunity deal, “I would never have testified, I would have pleaded the fifth.”

Anderson also said that in preparation for his testimony, the government provided him access to many documents needed to build the case against Stevens. At one point, Anderson claimed, prosecutors “set folders out on the desk and slid them away from me telling me I was not to read them. They left the room and closed the door. Of course I read them all.”

Stevens’ attorneys asked Judge Emmet Sullivan to call a hearing to investigate Anderson’s new claims, suggesting that the alleged misconduct was serious enough to warrant a dismissal of the charges against Stevens or a new trial.

A Justice Department spokeswoman declined to comment on the new motion.