The report, ordered by the government a year ago, is being closely watched as lawmakers around the world wrestle with the powerful tech firms' role in public life and their influence on everything from privacy to disinformation and traditional media.
The Australian Competition and Consumer Commission (ACCC) said in a preliminary report on the USA firms' market power that extra oversight was justified to ensure advertisers were treated fairly and the public access to news was unfettered.
The report noted it was "not at all clear" how Google or Facebook's algorithms chose which news stories or websites were shown to consumers first, and the platforms had "both the ability and the incentive" to favour businesses that paid to advertise on their platforms, limiting consumers' ability to make informed choices.
One of the recommendations includes a proposal to prevent a Google's Chrome browser and search engine being installed as default on mobiles, computers and tablets.
The ACCC believes the dominance of platforms like Google and Facebook justifies a greater level of regulatory oversight.
Some of the resulting investigations relate to allegations "that could sit under competition law which would go to issues of misuse of market power" while some relate to "issues of consumer law", Sims told a press conference.
The decline of traditional media has seen digital platform grow exponentially in the past decade.
It estimates the digital giants now scoop two-thirds of all Australian advertising spend. Google and Facebook - who derive a vast majority of their revenue from advertising - have captured 80 per cent of that growth in the Australian market.
The inquiry is looking at the broader social implications of the rise of digital platforms, such as issues of algorithm-driven news distribution and fake news.
Another recommendation being considered is for a specific code of practice for digital platforms' data collection to better inform consumers and improve their bargaining power.
The ACCC is considering whether an ombudsman should be established to deal with complaints about digital platforms from consumers, advertisers, media companies and other business users of digital platforms, the report revealed.
The competition watchdog is calling for a regulatory body to be given far reaching powers to investigate and monitor tech giants.
Around 94 per cent of online searches in Australia use Google, the ACCC's preliminary report says.
In its preliminary report, the ACCC said while digital platforms had revolutionised the way consumers communicated and accessed news and information and offered many benefits, there were questions about their the responsibility they held as "gateways" to information. Research commissioned as part of the inquiry indicates consumers are concerned about the extent and range of information collected by digital platforms, the Commission added.
Other areas identified for further investigation in the ACCC's preliminary report included signalling where news stories came from, obligations to delete users' data, whether users should be able to opt out of targeted advertising, and measures to fund news and journalism in Australia.
Tim Worner, chief executive of Seven West Media, publisher of The West Australian, said the ACCC report recognised the ways the power of Google and Facebook had harmed the local media and advertising industry.
The ACCC has requested further feedback on its recommendations and matters for review by 15 February 2019.