WASHINGTON - The Obama administration's plan to merge bank regulatory agencies will not solve future problems or promote efficiency in financial markets, the regulator of U.S. thrifts said on Wednesday.

John Bowman, the acting director of the Office of Thrift Supervision, also said the administration's plan to abolish his agency and the thrift charter would be unnecessarily costly.

We will not solve the potential problems of tomorrow by merging regulatory agencies, Bowman said in prepared remarks to be delivered at a House Financial Services Committee hearing.

He said the OTS should continue regulating thrift holding companies, but should not supervise systemically important conglomerates. OTS, which largely regulates mortgage lenders, was also the primary regulator for troubled insurer AIG. (Reporting by Karey Wutkowski; Editing by Julie Vorman)