Washington ? A controversial intelligence unit set up in the Pentagon provided skewed pre-war analysis to support Bush administration claims that Saddam Hussein was an ally of al-Qaida, an investigation by Democrats on the Senate Armed Services Committee has found.

The intelligence unit, run by Undersecretary of Defense for Policy Douglas J. Feith, shaded analytic judgments, ignored contrary evidence and sidestepped the CIA to present dubious findings to senior officials at the White House, the investigation concluded.

The report was released Thursday by Sen. Carl Levin, D-Mich., after a 16-month investigation conducted by Democratic staff members on the committee. Levin has been a persistent critic of Feith and the Bush administration on Iraq.

The report said that “intelligence relating to the Iraq-al-Qaida relationship was manipulated by high-ranking officials in the (Department of Defense) to support the administration’s decision to invade Iraq.”

Republicans criticized the report as politically motivated. “Senator Levin’s report is clearly a partisan effort to influence the upcoming election rather than an attempt to correct the flaws in our intelligence community,” said Sen. John Cornyn of Texas, a Republican on the Armed Services Committee.

The Defense Department issued a statement saying other investigations had found no evidence of wrongdoing by Feith’s office and that Levin’s report “appears to depart from the bipartisan, consultative relationship” between the Pentagon and Congress.

Feith, a lightning rod for critics of the Bush administration, was a leading proponent of the war in Iraq and was in charge of postwar planning. He has previously said that his office created the intelligence unit shortly after the Sept. 11 attacks to conduct a broad examination of state sponsors of terrorism.

The unit focused much of its energy on finding a link between Saddam and al-Qaida. Subsequent investigations, including that of the independent bipartisan Sept. 11 commission, have concluded that while there were contacts between Iraq and al-Qaida, there was no evidence of a collaborative relationship or Iraqi involvement in the Sept. 11 plot.

Much of the material in Levin’s report has been previously disclosed. But the 46-page document includes some new details that, according to Levin, show how Feith’s analysts repeatedly sought to outflank the CIA, which was much more skeptical of Iraq-al-Qaida ties.