Australia’s big media companies would be put under a “blow torch” under the federal Greens’ policy, which places breaking up the nation’s media concentration front and centre.

Sarah Hanson-Young said the Greens’ policy, finalised in the wake of the Christchurch terror attack and subsequent coverage, as well as the recent Tayla Harris trolling and response, would “reorient priorities” to put “public interest journalism and the public good” ahead of profits.

Any future media policy the Greens had influence over would have to cover a review of both the existing Australia media market, and its ownership, as well as the impact and effects of social media, Hanson-Young said.

“We are going to shine a light on the concentration of our news media with a Productivity Commission inquiry,” she said.

“And we’ll turn the microscope on the digital giants as well with a full review of social media.”

That would also mean establishing a public interest test, in line with the 2012 convergence review recommendations, which would impact any media company which had an audience of over 500,000 per month, a minimum revenue of $50m a year from its Australia’s media content and control of that media content.

Any mergers would need to take into account a diminishing of diversity in terms of unique ownership as well as content delivery and impact on editorial independence and “likely impact on the fair and accurate presentation of news”.

An inquiry looking into how to break up Australia’s media concentration would be a priority, with the Greens wanting the Productivity Commission to review “the health of our news media and make recommendations about what role the commonwealth can and should have in ensuring that health”.

That would include a review of the current media ownership breakdown, the role and powers of regulators, as well as a beefing up of those powers, particularly for the Australian Communications and Media Authority.

Hanson-Young said the safeguards Acma has set up around what can and can’t be broadcast had not kept up with the times, meaning Acma is powerless to regulate websites and social media linked to broadcasters.

“The Greens support expanding the definition of community safeguards used by the Acma to include the public from content that maligns a person or persons based on certain immutable characteristics,” Hanson-Young said.

“All news and commentary in Australia should maintain a high standard of truthfulness and journalistic ethics. That’s why we support the Acma having greater powers over subscription and streaming services. Subscription services like Sky News and online news streaming should not have a lower level of scrutiny, especially when they are broadcast in so many public spaces and so many people are moving to consuming their news online.”

Under the Greens’ proposal, Acma would have responsibility for media from free-to-air to subscription (cable) and streaming services and be given increased enforcement powers “so they are able to step in when the line is crossed to ensure hate speech does not infiltrate mainstream news, whatever medium it comes through”.

Making news subscriptions tax deductible as well as introducing a deductible gift recipient status for eligible news organisations is also on the Greens’ agenda.

Social media and digital media would be subject to its own inquiry, looking at how the platforms upheld “the rights and protections of their users and contributing to public discourse”, how complaints were handled and what standards needed to be set.

“With the concentration of power in the hands of a few and virtually no rules to govern what they do with the power, it’s clearly time to have a public debate about the role and regulation of the digital space,” Hanson-Young said.

There, the Greens are not alone. The Morrison government has turned its attention to the power of social media and digital giants in the wake of the Christchurch attack, with Labor having also called for changes to “dated media policies” which don’t take into account new technologies and platforms.

Mitch Fifield oversaw reforms, left over from Malcolm Turnbull’s turn as communications minister, which abolished the two out of three rule, which had prevented a single media company owning a commercial radio station, TV station and newspaper in the same licence area.

Labor has promised a more comprehensive approach, having previously accused the government of “piecemeal” policy.