The new rules will specifically target app stores, search engines, e-commerce sites and hotel booking websites like Expedia, requiring them to be more transparent about how they rank search results and why they delist some services.
The proposal would also give companies the right to collectively sue online platforms if they do not respect the new rules on non-discrimination and transparency.
Separately, tech giants such as Facebook and Google will have to decisively step up their efforts to tackle the spread of fake news online in six months or potentially face further regulation from the European Union.
The European Commission will draw up an EU-wide Code of Practice on Disinformation by July with measures to prevent the spread of fake news such as increasing scrutiny of advertisement placements, it said on Thursday.
EU policymakers are particularly worried that the spread of fake news could interfere with European elections next year, after Facebook disclosed that Russia tried to influence US voters through the social network in the run-up to the 2016 US election. Moscow denies such claims.
Advertisers and online platforms should produce "measurable effects" on the code of practice by October, failing which the Commission could propose further actions, including regulation.
Companies will have to intensify efforts to close fake accounts and put in place measures to reduce revenues for purveyors of disinformation and restrict targeting options for political advertising.
© Thomson Reuters 2018