WASHINGTON -- The Treasury Department's surprise Christmas Eve move to uncap the potential aid to Fannie Mae and Freddie Mac should be investigated, lawmakers from both political parties said Wednesday.

Rep. Dennis Kucinich (D., Ohio) said his congressional subcommittee plans to investigate Treasury's decision to lift the existing $400 billion cap on government cash available to the two firms. Separately, Reps. Scott Garrett (R., N.J.) and Spencer Bachus (R., Ala.) called for the House Financial Services Committee to hold...