The Federal Bureau of Investigation has expanded its use of a controversial section of the Patriot Act to gather information more than 50 times in a three-year period, according to a new internal review released as Congress debates whether to let the law expire.

The FBI’s use of Section 215 of the Patriot Act “continues to expand,” according to the report released Thursday by the Justice Department’s Inspector General Michael Horowitz. The expansion is in part because the legal threshold for its use has been lowered and because society’s use of the Internet has also “expanded the quantity and quality of electronic information available to the FBI,’’ the report states.

The report also faulted the FBI for taking seven years to finalize some privacy protections within the data searches. A Justice Department spokesman said the agency has worked carefully “to ensure that these revised procedures appropriately protected privacy and civil liberties while allowing the government to obtain and use vital foreign intelligence information.’’

American Civil Liberties Union lawyer Alex Abdo said the report “adds to the mounting evidence that Section 215 has done little to protect Americans and should be put to rest.’’

Section 215 authorizes the government to collect “tangible things” such as business records with an order from the Foreign Intelligence Surveillance Court.