Sergeant Bowe Bergdahl
Sergeant Bowe BergdahlReuters

A new congressional report seen by The Washington Post says the 2014 prisoner swap, in which five Taliban prisoners were released in exchange for American captive Sgt. Bowe Bergdahl was “illegal”, the newspaper reported Thursday.

After a year-and-a-half-long investigation, the House Armed Services Committee’s Republican majority renewed assertions that the decision to send the senior Taliban figures to Qatar without notifying Congress violated several laws.

It also misled lawmakers in a way that “severely harmed” the administration’s ties with lawmakers, the report found, according to The Washington Post.

Republicans questioned the prisoner exchange soon after it took place, with Senator John McCain saying the administration may not have acted properly in releasing the terrorists.

"These are the highest high-risk people. Others that we have released have gone back into the fight. That's been documented. So it's disturbing to me that the Taliban are the ones that named the people to be released," he said at the time.

The Washington Post noted that the prisoner exchange ignited a storm of criticism whose effects are visible today, as the White House struggles to build congressional support for resettling some Guantanamo prisoners overseas and bringing others to the United States.

While administration officials hope to help Obama deliver on his promise to close Guantanamo Bay before he leaves office, lawmakers appear unlikely to drop long-standing their opposition.

The controversy over the transfer was compounded by revelations that Bergdahl walked off his small Army outpost in southeast Afghanistan in 2009. Bergdahl, who was held under difficult conditions in Pakistan for five years, is now facing desertion charges in a military court.

During the investigation, committee staff reviewed over 4,000 pages of documents, including numerous emails between administration officials; conducted interviews; and visited Qatar, where government officials made arrangements to monitor the Afghans after their release.

By February 2014, the report says, the administration had already solicited a proof-of-life video of Bergdahl as a step toward a potential swap, and officials were advancing their discussions with their Qatari counterparts. News reports had surfaced suggesting that a renewed push to secure Bergdahl’s release had begun.

“Yet, the Department did not convey any of the details to the Committee,” the report stated, according to The Washington Post. “Indeed, [a Taliban statement to the Associated Press] contained more specifics about a prospective exchange than what was conveyed through official channels to the Committee and others in Congress at the time.”

Around the same time, then-Pentagon General Counsel Stephen Preston was helping prepare then-Defense Secretary Chuck Hagel for budget testimony. According to the report, Preston proposed the following response if Hagel was asked about the subject: “As for recent reports, let me just say this: ‘We have not been involved in active negotiations with the Taliban recently, but SGT Bergdahl’s return is an issue we would like to discuss with the Taliban if and when such talks are restarted.'”

Lt. Col. Joe Sowers, a Pentagon spokesman, said Preston’s suggested response for Hagel was “accurate and forthcoming”, adding the comments were appropriate for an unclassified setting and reflected the preliminary stage where the issue stood at that moment.

The report also does not put to rest the debate about the legality of the transfer, notes The Washington Post. After the transfer,  the Government Accountability Office determined the administration violated the 2014 National Defense Authorization Act by failing to give 30-day notice and also the Anti-Deficiency Act because it used money for that purpose.

A senior administration official said, however, that notifying Congress could have endangered Bergdahl’s life.