Journalists would be compelled to reveal their sources before State Parliament under amendments to so-called shield laws that have delayed the long-awaited legislation yet again.
The Government was due to debate the laws in the Upper House yesterday but changed its mind at the last minute, saying it needed more consideration by Cabinet.
Under the laws in their original form, journalists hauled before a legal institution would not have to give evidence if they had promised anonymity to a source.
Crucially, the privilege would have extended not only to courts, but other legal settings such as tribunals, the Corruption and Crime Commission and parliamentary hearings.
The laws hit a snag in November when Greens MP Giz Watson referred them to an Upper House committee, which recommended the privilege not apply to parliamentary proceedings.
The Government indicated it would support that view before pulling the legislation from debate.
Shadow attorney-general John Quigley said if politicians were going to pass a law requiring every other judicial institution to respect protections for journalists, then Parliament should set the example.
"Media play the central role in our democracy of bringing governments and the bureaucracy to account and journalists' code of ethics requires them to protect their sources," he said.
"But under the amendments, a government could, and is likely to, say, 'You have not revealed your source to the CCC, you will come up to a parliamentary committee and reveal it to us', which is an outrage."
Curtin University's head of journalism, Joseph Fernandez, said he was disappointed to learn of the amendment.
"Journalists have been seeking a presumption favouring the protection of their confidential sources for a very long time and the original Bill provided that presumption," he said. "That presumption has now been unnecessarily diluted."
Attorney-General Michael Mischin said the Government remained committed to the laws.