After a 16-month antitrust investigation, a U.S. House subcommittee released a detailed report Oct. 6 accusing major online platforms of having monopoly power and recommending structural separations of certain businesses.

The 449-page report concluded that all four companies investigated by the subcommittee — Facebook Inc., Alphabet Inc.'s Google LLC , Amazon.com Inc. and Apple Inc. — either have a monopoly or "durable market power" in a specific market.

Notably, the report contains the views and conclusions of subcommittee staff, which is Democratic led, and does not claim to represent the views of members of the subcommittee.

Facebook has a monopoly in the social networking market, according to the report. The company "used its data advantage to create superior market intelligence to identify nascent competitive threats and then acquire, copy, or kill these firms," the subcommittee concluded.

The company "competes more vigorously among its own products — Facebook, Instagram, WhatsApp, and Messenger — than with actual competitors," wrote the subcommittee staff.

The subcommittee concluded that Google has a monopoly in online search and search advertising.

"Google's dominance is protected by high entry barriers, including its click-and-query data and the extensive default positions that Google has obtained across most of the world's devices and browsers," the subcommittee concluded.

Amazon has "significant and durable market power in the U.S. online retail market," the subcommittee found after interviewing third-party sellers, brand manufacturers, publishers and other market participants.

The subcommittee also concluded that Apple "exerts monopoly power in the mobile app store market, controlling access to more than 100 million iPhones and iPads in the U.S."

Collectively, the subcommittee found, the impact of this perceived market power has led to the decline of trustworthy sources of news and weakened U.S. innovation and entrepreneurship and resulted in persistent collection and misuse of consumer data.

However, Amazon criticized the report, describing it as "regulatory spit-balling on antitrust."

"We believe competition is good for our economy, good for small businesses, and good for customers. This flawed approach for regulating retail stores fails to consider the unintended impacts on all three," the e-commerce giant said in a blog post.

The subcommittee issued three big-picture recommendations to address the perceived problems: actions that can be taken to restore competition in the digital economy; actions to strengthen the antitrust laws; and ideas for reviving antitrust enforcement.

As part of recommendations to restore competition in the digital economy, the subcommittee recommended that "Congress consider legislation that draws on two mainstay tools of the antimonopoly toolkit: structural separation and line of business restrictions." Notably, structural separations do not necessarily mean forcing a sale. There are two forms of structural separation: ownership separations, which do require a divestiture and separate ownership of each business; and functional separations, which permit a single corporate entity to engage in multiple lines of business but create hard boundaries between them.

The subcommittee also recommended that Congress consider shifting presumptions for any future acquisitions by the companies, so that any deal would be presumed anticompetitive "unless the merging parties could show that the transaction was necessary for serving the public interest and that similar benefits could not be achieved through internal growth and expansion." This process would occur outside the current Hart-Scott-Rodino Act process and would require the companies to report any and all transactions.

Among the recommendations to reform antitrust laws are recommendations to strengthen sections of both the Clayton Antitrust Act and the Sherman Act, two core federal antitrust laws.

Among the recommendations for reviving antitrust enforcement are triggering civil penalties for "unfair methods of competition" rules, requiring the U.S. Federal Trade Commission to collect data on concentration and require regular merger retrospectives.

In addition to possible recommendations for legislative reform, the committee's report could also be used as evidence against the companies in court.

The top Republican on the subcommittee, Rep. Jim Sensenbrenner, R-Wis., said on Oct. 1 that while Congress needed to grasp what the four companies do with their size and influence, Congress is "ill-suited to micromanage the economy," suggesting he is opposed to the recommendations.

Multiple reports say the Republican side will release two separate reports to complement the release of this report.

Rep. Ken Buck, R-Colo., is expected to lead the release of a report called "The Third Way," which could be supported by other House Republicans, Axios reported Oct. 6.

Buck reportedly told Axios that while he agrees with many of the conclusions from the Democratic-led report, he is opting to release a different report.

Reports say that Rep. Jim Jordan, R-Ohio, the ranking member on the House Judiciary subcommittee, will also release a separate report that focuses on allegations of conservative bias on tech platforms. Jordan has consistently raised the allegations in hearings pertaining to large online platforms.