Democratic U.S. Senate candidate Paul Van Dam on Tuesday called for Congress to establish an independent investigation into the abuse of Iraqi prisoners. He said his opponent, U.S. Sen. Bob Bennett, R-Utah, discounts the need for such an investigation.

But a spokeswoman for Bennett said an "aggressive inquiry" is already being conducted.

"Senator Bennett condemns the inhumane treatment of Iraqi prisoners by U.S. personnel," the senator's spokeswoman, Mary Jane Collipriest, said. "The investigation into these abuses is already under way — both in the Congress and at the Pentagon — and Senator Bennett is supportive of this aggressive inquiry."

Van Dam, who served a term as Utah attorney general and was a member of the Army's Judge Advocate General's Corps, said allowing the military to investigate itself gives the appearance of a cover-up.

"As a former member of the Army's JAG Corps, I realize the importance of maintaining high standards of conduct and accountability in our armed forces," Van Dam said. "For our military to be effective, it must have the respect and admiration of other nations."

Van Dam said failures in the chain of command that allowed the abuses to occur must be examined more thoroughly than is being done by the Senate panel now holding hearings on the issue.

"My opinion is, it's that important. If something like this had been discovered at the Utah State Prison, you can bet that would happen," he said. "This has to be dignified by a congressional investigation."

Collipriest said the ongoing inquiry has already lead to charges being brought against one individual "involved in these outrageous acts." Other courts-martial are expected in coming days.

Those proceedings could involve some high-ranking officers, she suggested.

"As the investigation continues, Senator Bennett believes it is very likely that many more court-martial proceedings will be called against other prison guards and their commanders, but also others farther up the chain of command."