Updated

A former senior investigator on the Independent Inquiry Committee (search) who thinks the panel has gone too soft on U.N. Secretary General Kofi Annan (search) in its Oil-for-Food investigation has been called to testify before Congress next week.

Rep. Chris Shays (search), chairman of the House Government Reform's Subcommittee on National Security, Emerging Threats and International Relations, issued a subpoena to Robert Parton (search) on Thursday. Parton on Wednesday night handed over documents relating to the investigation after he was issued a subpoena by another panel, the House International Relations Committee, on April 29.

"He [Parton] did decide to leave his work because he didn't agree with the findings of the report" regarding who is to blame in the $64 billion scandal released by the IIC in March, Shays told FOX News on Friday.

Parton and another IIC investigator, Miranda Duncan (search), left the panel headed by Paul Volcker (search) in mid-April. They accused the IIC of downplaying Annan's role in the scandal in an interim report released by the panel last March.

"The whole reason why the Volcker report was taking place was to bring confidence to the U.N. ... we would learn the good, the bad and the ugly. The bottom line is, we don't really have confidence in that report," Shays said.

Not only is Shays requesting documents and other information relevant to the probe of the $64 billion program, but he's also calling on Parton to appear before his committee for a hearing on Tuesday at 2 p.m. EDT.

"We expect that Mr. Parton will meet his legal obligation to comply with the subpoena. As an experienced investigator and seasoned law enforcement professional, Mr. Parton is acting responsibly by coming forward to help augment the public record on matters too long shrouded in secrecy," the Connecticut Republican said in a statement.

Shays said his panel tried to work with the IIC on ways, short of a subpoena, to evaluate the information Parton can provide about "key pieces of evidence regarding U.N. contracting." Neither the IIC nor the United Nations should stonewall the effort, he warned.

"I think Mr. Volcker ... should just let this gentleman speak to Congress," Shays told FOX News. "Mr. Volcker believes, basically, all the evidence was presented in the report. They just disagree on the conclusion of that evidence."

Click here to read Shays' letter to Volcker (pdf file).

Lawmakers: Immunity Out

Congressional lawmakers have been trying to talk to Parton ever since his resignation. Last week, Volcker tried to block such efforts by insisting that Parton and Duncan, both Americans, had diplomatic immunity.

As senior investigative counsel, Parton was responsible for investigations into the procurement of companies under the Oil-for-Food program and he was the lead investigator on issues pertaining to allegations of impropriety relating to Kofi Annan and his son, Kojo Annan (search). Duncan worked on Parton's team.

Last week, a spokesman for Volcker denied he was invoking diplomatic immunity (search) to protect the panel or the United Nations, saying the calls to the committees were made out of "courtesy."

Shays said immunity should be out of the question, since fighting over such "legalese" would not help restore confidence in the world body.

"We just want transparency, we're used to it in the United States. We have freedom of information, we don't have that in the U.N.," he said. "There will be no faith in the U.N. until all the facts are out ... everyone is cooperating, and people aren't cooperating."

House International Relations Committee Chairman Henry Hyde (search) on Thursday said he directed his own investigators to begin "immediate and careful examination" of documents given to them by Parton this week.

"It is my hope and expectation that neither the United Nations nor the independent inquiry will attempt to sanction Mr. Parton for complying with a lawful subpoena," the Illinois Republican said.

The contents of the boxes handed over by Parton are believed to be damaging to the secretary-general because, as sources told FOX News, they describe inconsistencies in the story Annan told investigators about a conflict of interest involving Kojo Annan and Cotecna (search), the Swiss company that employed Kojo Annan and which won one of the most lucrative Oil-for-Food contracts.

Volcker wrote a letter to Parton's lawyer on Thursday as well as to Shays, saying that turning over any investigation-related documents violated confidentiality agreements and that the IIC is contemplating action on the matter.

Click here to read Volcker's letter to Parton's lawyer (pdf file).

Click here to read Volcker's letter to Shays (pdf file).

IIC staffers "cannot, in my judgment, reasonably and honorably unilaterally violate those pledges of confidentiality and acceptance of immunity at the expense of their former colleagues and the investigation itself," the letter to Shays reads.

After the first subpoena was issued, Parton's attorney, Lanny Davis (search), said he wrote to the United Nations and Volcker asking if they would instruct Parton to defy a congressional subpoena. After not hearing back from the United Nations and the IIC, Parton handed over the boxes of documents to Hyde's committee.

Volcker: Parton Violated Confidentiality

Volcker issued a statement Thursday saying his panel's work "requires confidentiality with respect both to sources who have entrusted the inquiry with vital information and to the committee’s own deliberations.

"I am confident that our report contains all the relevant factual information gathered by my investigative team concerning Secretary-General Annan and his son," Volcker said, referring to Kojo Annan.

"It is only the inferences drawn from those facts that are subject to different conclusions and where two former staff members may have disagreed. However, it is the committee’s responsibility to draw the conclusions from the facts that we believe are most appropriate. In any event, at the end of the day, the facts must speak for themselves."

Volcker noted that in his letter responding to Shays', he cited the need to proceed with congressional inquiries with caution "in order to preserve the integrity of our investigation."

"In keeping with protections afforded to investigatory bodies, including in the U.S., I stressed that, 'in particular, all investigations that confront serious allegations of fraud, corruption, misuse and mismanagement must enjoy a degree of secrecy as evidence is being gathered.' This issue goes to the heart of our ability to follow investigative leads and develop investigative information," Volcker said in the statement.

Volcker distributed copies not only of his response letter to Shays, but also the letter sent to him on Wednesday by Davis and Volcker's response to Davis' letter.

In his correspondence with the IIC and the United Nations, Davis notes that he had only about an hour to respond to the subpoena after it was issued on Friday. He said the committee instructed Parton not to tell either the IIC or the United Nations about the subpoena until he fully complied with it. That compliance occurred on Wednesday night. Davis noted that on Monday, he wrote to Volcker asking for direction on how Parton should respond to such a summons.

Click here to read Davis' correspondence (pdf file).

"Notwithstanding Mr. Parton's requests for such instructions, by letters dated May 2 and May 3, 2005 (attached), neither of you [Volcker or IIC counsel Susan Ringler] directed Mr. Parton to defy a congressional subpoena and, indeed, neither of you responded entirely to the two questions I asked," Davis wrote.

Volcker wrote to Davis on Thursday, saying he did not receive the lawyer's request for instruction or the copy of the subpoena until that day, May 5.

"Most disturbingly, if Mr. Parton did in fact produce IIC related records, this was done without any discussion with the IIC," Volcker wrote. "Mr. Parton's production of any IIC related documents violated his individual confidentiality agreements with the IIC and the U.N."

Volcker went on to say that the IIC and U.N. did in fact answer Davis' questions but that the lawyer "chose to ignore" that direction, calling him "disingenuous."

"The committee is reviewing this matter and its options," he added.

Volcker, the former chairman of the Federal Reserve, was appointed last year by Annan to head up the investigative panel into the Oil-for-Food program. So far, Volcker's panel has released two interim reports that say the program suffered from mismanagement and raise questions about the role of Kojo Annan. A final report is expected to be released this summer.

After the release of the second report, Parton and Duncan resigned as investigators, objecting to the committee's handling of Annan's dealings with Cotecna.

"Contrary to recent published reports, I resigned my position as senior investigative counsel for the IIC not because my work was complete but on principle," Parton told The Associated Press in a statement at the time of his resignation.

FOX News' Jonathan Hunt and Per Carlson contributed to this report.