Washington ? A simmering political struggle behind the Senate inquiry into prewar intelligence on Iraq boiled over publicly Tuesday with the disclosure of a Democratic memo outlining strategies for “exposing the administration’s dubious motives” behind the war.

The leaked memo, which was prepared by the staff of Sen. Jay Rockefeller, D-W.Va., the vice chairman of the Senate Select Committee on Intelligence, discusses ways that Democrats can steer the existing inquiry toward taking a more critical look at the White House.

It also indicates that Democrats intend to launch a separate independent investigation of the administration’s use of intelligence as the parties head into the height of the presidential election season next year.

“Intelligence issues are clearly secondary to the public’s concern regarding the insurgency in Iraq,” the memo says. “Yet we have an important role to play in revealing the misleading, if not flagrantly dishonest, methods and motives of senior administration officials who made the case for unilateral pre-emptive war.”

The tone of the memo could be embarrassing to Democrats and provides new ammunition for Republican complaints that Democrats are seeking to use the inquiry for political gain.

Sen. Pat Roberts, R-Kan., the chairman of the intelligence committee, described the memo as a “slap in the face” to the bipartisan traditions of the committee and called the plan an effort to undercut the panel’s investigation.

“It’s an attack plan,” Roberts said late Tuesday in an interview on Fox News Channel.

In a statement released by his press office, Roberts said the memo “exposes politics in its most raw form. … It’s a purely partisan document that appears to be a road map for how the Democrats intend to politicize what should be a bipartisan objective review of prewar intelligence.”

Rockefeller also released a statement, acknowledging that the memo was written by his staff, but saying that it had not been approved “nor was it shared with any member of the Senate Intelligence Committee or anyone else.”

“Having said that,” Rockefeller added, “the memo clearly reflects staff frustration with the conduct of the … investigation and the difficulties of obtaining information from the administration.”

The disclosure is the latest sign of discord and partisan maneuvering on the committee, which began its investigation of the prewar intelligence on Iraq this summer.

Roberts has repeatedly indicated that he would like to limit the investigation to examining the performance of the CIA and other agencies, and has angered Democrats by making comments to the media suggesting that the probe is already “90 to 95 percent” finished and that certain conclusions have already been reached.

Democrats have argued that the probe should not be confined to the performance of the intelligence agencies, but should also examine whether the administration pressured analysts to reach certain conclusions or misrepresented intelligence findings to the public.