The federal investigation of former U.S. Sen. Ted Stevens was “permeated by the systematic concealment” of evidence that would have aided the Alaska politician’s defense at trial and would have “seriously damaged the testimony and credibility of the government’s key witness,” a special prosecutor concluded.

The 514-page report was a response to an investigation ordered by U.S. District Judge Emmet G. Sullivan, who threw out Stevens’ April 2009 guilty verdict in a financial disclosure case after the Justice Department revealed that prosecutors kept key information from defense attorneys.

Three years later, “special prosecutor” Henry L. Schuelke made the report public over objections from the prosecutors involved in the case.

Prosecutors are generally required to turn over helpful evidence to defense lawyers.

Stevens, an Alaska Republican who died in a small-plane crash in 2010, lost his reelection bid shortly after being convicted of seven counts of making false statements on financial disclosure statements to hide about $250,000 in gifts and free renovations to his Alaska house.

The results of Schuelke’s investigation were made public in a November order by Sullivan. In the report made public this morning, Schuelke wrote that his team examined and analyzed “well over 128,000 pages of documents, including the trial record, prosecutors’ and agents’ emails, FBI 302s and handwritten notes, and depositions of prosecutors, agents and others involved in the investigation and trial.”

In the end, however, Schuelke recommended against charging the federal prosecutors — Brenda Morris, William Welch, Edward Sullivan, Joseph Bottini and James Goeke, as well as Nicholas Marsh, who committed suicide last year — with a crime. He

wrote that prosecuting the Justice Department lawyers would be difficult because Sullivan never issued a “clear, specific and unequivocal order” to disclose evidence that would have helped the defense.

Read more: The Post’s crime coverage