Australia’s media companies have used Scott Morrison’s words to intensify arguments against politicians being the final arbiter of whether journalists are prosecuted for disclosing sensitive information in the public interest.

The major media organisations have written to all federal parliamentarians to back in a new campaign protesting against tranches of national security legislation penalising whistleblowing and, in some cases, criminalising journalism. The campaign kicked off this week, with outlets producing blacked out front pages to draw attention to restrictions on public interest journalism.

The companies noted in the new letter to MPs that Morrison told parliament on Monday that Australians would not want to live in a country where politicians on a whim could decide who gets prosecuted and who doesn’t – an observation the prime minister made during question time.

“We couldn’t agree more. And yet we do live in that country,” the letter to parliamentarians says. “The attorney general – a politician – has the power to decide if journalists will be prosecuted.”

The current system gives the attorney general capacity to send a direction to the commonwealth director of public prosecutions and request they seek consent before a prosecution. The attorney general, Christian Porter, signed a directive to the commonwealth DPP on 19 September.

Labor this week has backed the push by media companies, through the “right to know coalition”, for journalists to be exempted from laws that could see them jailed for doing their job.

The shadow treasurer, Mark Dreyfus, said on Monday Labor supported that as “an appropriate legislative change, and the government ought to be bringing in legislation into the parliament to do that, because clearly this government hasn’t understood the discretions that are there”.

Dreyfus said the change he supported would not be a blanket exemption, but “recognising the vital role that’s played by journalists in our democracy and saying that it should not be possible to charge someone who is merely doing their work as a journalist and reporting on matters in the public interest”.

“That’s what it would look like.”

The media companies have told MPs the government in recent years has passed too many laws that favour secrecy over openness.

“They are at odds with the expectation that we live in an open and transparent society,” the letter says. “Like the prime minister, we do not believe an individual politician should be placed in the dangerous position of being the final arbiter on whether or not a person should be prosecuted.

“We believe that laws that put a politician in this compromising position should be amended so this situation does not arise.”

When asked by Anthony Albanese on Tuesday to explain how he reconciled his observation in question time on Monday with the reality that a politician is the decision-maker under the current framework, Morrison said the Labor leader needed to pay attention to his entire answer.

“If he’d paid attention to the entire response I gave yesterday he would have understood that the point about the prosecution of journalists is not the attorney general is required to give consent, but that the ALP is asking us to rule out consent even before any advice is received from any of the relevant agencies – which would be unprecedented and most likely unlawful,” the prime minister said.

Morrison said the process required “investigative authorities to look at these matters, to hand that over to prosecution authorities, and then there is a process for the attorney general”.

“But what the leader of the opposition wants to do is throw that all away and he wants to make the decision if he were prime minister about who gets prosecuted or who doesn’t even before those agencies … have even considered the matter.”

Media companies argue in their letter to MPs that journalists are not seeking a blanket exemption from national security laws. “We are asking for common sense changes to laws so that, like politicians, the unique role journalists have in serving society is acknowledged.”

The companies are asking for the right to contest the application for warrants for journalists and media organisations; exemptions for journalists from laws that would put them in jail for doing their jobs; adequate protection for public-sector whistleblowers; a new regime that limits which documents can be stamped secret; a properly functioning freedom of information regime; and defamation law reform.