The Queensland transport department has been accused of failing to justify the need for audio recordings in taxis 20 months after floating the idea.
The state's former Labor government released a discussion paper on the proposal in May 2011.
Cameras were introduced in cabs in 2006, but audio recordings weren't allowed.
With submissions closing on Friday, the Queensland Council for Civil Liberties said the Department of Transport and Main Roads had failed to produce evidence showing that audio recordings would improve driver safety.
"Despite having at least 18 months to do so, the department with the significant resources at its disposal has failed utterly to produce any cogent evidence which would justify its proposed invasion of personal privacy," the council said in its submission.
He added the department's discussion paper said nothing on this issue.
A spokeswoman for the department said the government would consider the community's views in coming months.