WASHINGTON — The Obama administration and the nation’s chief privacy regulator pressed Congress on Wednesday to enact online privacy legislation, saying new laws would level the playing field between companies that already had privacy policies and those that lacked them, and thus escape regulatory oversight.

Jon Leibowitz, chairman of the Federal Trade Commission, which enforces limited Internet privacy laws, and Cameron F. Kerry, general counsel for the Commerce Department, said at a hearing of the Senate commerce committee that writing new laws and giving the F.T.C. the power to enforce them with civil penalties would promote Internet commerce by increasing the trust that Americans put in online transactions.

Currently, the F.T.C. monitors whether Internet companies that have privacy policies keep their promises to consumers about when and where they will share personal information. But the commission lacks the authority to assess penalties for most transgressions, and it has little authority over how companies operate when they have no written privacy rules.

“Granting direct enforcement authority to the F.T.C. would enable the commission to take action against outliers and bad actors even if their actions do not violate a published privacy policy,” Mr. Kerry said, according to written testimony released at the beginning of the hearing.