The report by the staff of the FTC's competition bureau argued that the owner of the world's No. 1 Internet search engine illegally took information from rival websites to improve its own search results and placed restrictions on websites and advertisers. The report recommended suing Google for several of its business practices.
The FTC settled its multiyear investigation of Google in 2013, concluding that the company had not manipulated its search results to hurt rivals.
Details of the report, which the Journal said were inadvertently disclosed in an open-records request, come as European antitrust regulators decide their next steps in a four-year investigation of Google.
Google said in a statement that "after an exhaustive 19-month review, covering 9 million pages of documents and many hours of testimony, the FTC staff and all five commissioner agreed that there was no need to take action on how we rank and display search results."
"Speculation about potential consumer and competitor harm turned out to be entirely wrong," Google said.
A representative of the FTC said the agency had no comment on the report.