Media organisations including the ABC, SBS, News Corp Australia, The Guardian and Nine Entertainment issued the warning to senators on Tuesday, saying the changes as drafted could have a chilling effect on news coverage and inspire frivolous lawsuits.
But some digital privacy advocates urged senators to pass the changes into law, saying Australian privacy rules were decades out of date and the need for reform had grown urgent.
The Senate inquiry, called in September, is tasked with reviewing the first tranche of changes to the Privacy Act, including penalties for serious privacy invasions and doxxing.
The draft law also includes exemptions for media outlets and journalists, but Nine executive counsel Kiah Officer said the changes did not offer enough protection and would allow powerful people to shut down stories they did not like.
Similar rules in other countries, including the UK, showed privacy laws would not be used by everyday people, she said, but would become "de facto defamation laws".
"(Laws like this) very much become tools of celebrities, politicians and wealthy public figures to essentially stifle the publication of information that might be at odds with whatever public persona they seek to portray," Ms Officer said.
"There is a real public interest in limiting the ability of people to stifle those reports and also to utilise the courts in order to suppress examinations of their activities."
The threat of more lawsuits would have a chilling effect on news outlets, Free TV Australia chief executive Bridget Fair said, and could make small organisations, in particular, reticent to pursue important stories.
"We've seen a complete explosion in the use of defamation claims as a means of trying to shut stories down and we've also seen an explosion of costs, up to companies spending $30 million-plus defending defamation claims," she said.
"We have a defamation claims industry in this country - we do not want to replicate that in the privacy arena."
News Corp policy and government affairs head Georgia-Kate Schubert said the proposed changes would have to be replaced to give media organisations certainty.
"We do not think that the proposed drafting is at all redeemable to address our concerns," she said.
But privacy advocates told senators the proposed changes should be approved quickly, and Digital Rights Watch chair Elizabeth O'Shea said the exemptions for media outlets were "significantly broad".
"We think there is a real urgency around privacy reform, in part because the current act is so significantly out of date," she said.
Human Technology Institute co-director Professor Edward Santow, from the University of Technology, Sydney, said consultation, proposals and inquiries into privacy law reforms stretched back to 2005 and the public could not afford further delays.
"We've got two choices: either go forward with this bill with some sensible amendments or delay and defer," Prof Santow said.
"Clearly, it will be better to move forward with this bill with those sensible amendments."
The Senate committee is expected to issue its findings in November.
