The report said Brown ignored the new but untested National Response Plan, ignored or went around his direct superior and called the White House directly, The Washington Post reports.
Brown resigned shortly after Katrina devastated much of the U.S. Gulf Coast amid accusations he failed as head of FEMA.
The report is a supplement to a Feb. 15 report released by an all-Republican panel called "A Failure of Initiative," which laid blame on a variety of federal, state and local government officials.
It said Brown didn't report to Homeland Security Secretary Michael Chertoff like he was supposed to.
Rep. Thomas M. Davis III, R-Va, the chairman of the panel, called for FEMA to be re-evaluated but not the disaster plan.
He said it wasn't given a chance to be tested.
A House committee is currently reviewing Katrina relief efforts and a Senate panel is working on their own report.