WASHINGTON (CNN) -- Democrats will aggressively investigate pre-Iraq war intelligence failures if they win back the Senate, a Democratic leader said Friday.

While releasing a report on U.S. contracting problems with the Iraq war -- which he called "the most significant waste, fraud and abuse in the history of the country," Senate Democratic Policy Committee Chairman Byron Dorgan said Democrats will hold "aggressive oversight hearings" on pre-war intelligence, contracting, and a other issues related to the war.

"There's no question that we will finally understand what happened," with intelligence failures, the North Dakota Senator said.

Asked about Republican concerns that Democrats want to get back at Republicans -- possibly even impeach President Bush -- Dorgan said, "it's not retribution," but an attempt to make up for Republicans who "abdicated oversight" of the war because they have "one party control and no one wants to embarrass anyone."