House Republican lawmakers fired the opening salvo Monday in a war they plan against the Consumer Financial Protection Bureau created by this year's overhaul of financial regulations.

Republican Reps. Spencer Bachus of Alabama, the leading contender to take the reins of the House Financial Services Committee, and Illinois Rep. Judy Biggert, the top Republican on the panel's oversight and investigations subcommittee, sent letters to the inspectors general of both the Treasury Department and the Federal Reserve, directing them...