The nation’s top copyright official made a blistering attack Thursday on a controversial legal settlement that would let Google create a huge online library and bookstore.

Testifying before the House Judiciary Committee, Marybeth Peters, the United States register of copyrights, said the settlement between Google and groups representing authors and publishers amounted to an end-run around copyright law that would wrest control of books from authors and other right holders.

Ms. Peters, the first government official to address the settlement in detail, said it would allow Google to profit from the work of others without prior consent and that it could put “diplomatic stress” on the United States because it affected foreign authors whose rights are protected by international treaties.