MPs are due to vote on controversial measures to tighten newspaper regulation, which critics fear could suffocate the free press.
Parliament will have its say on two amendments to the Data Protection Act on Wednesday.
The first amendment was tabled by former Labour leader Ed Miliband in response to the Government's decision not to launch the second stage of the Leveson Inquiry.
If it goes through, the amendment would see a new statutory inquiry into the media.
The second amendment would see the introduction of a cost measure forcing all publishers not signed up to a state-backed regulator to pay their own and their opponent's legal costs in relation to alleged data breaches.
The requirement to pay costs - which was tabled by Labour deputy leader Tom Watson - would stand even if the publisher won.
Prime Minister Theresa May's official spokesman said that Mrs May told Cabinet it was "very important for the Government to resist amendments which could undermine our free press".
Almost £50 million of public money has been spent on investigating phone hacking, and the PM told ministers that establishing a further public inquiry, requiring great time and expense, would not be a "proportionate" solution to allegations that have already been the subject of several extensive police investigations or ongoing investigations by the Information Commissioner's Office, said the spokesman.
The Government remained committed to a voluntary system of press self-regulation, Mrs May told Cabinet.
Local newspaper editors have said that if passed, the amendments to the bill could destroy regional journalism.
In a joint statement released by the News Media Association they described the measures as draconian, adding that they would cause irreparable damage to the sector.
The vote is due to take place on Wednesday afternoon.