A Labor and Greens-dominated probe into the $80 million survey that ended with a majority "yes" result said in the report, released in February, that the bureau was forced to divert staff from other projects to run the national survey, and that it had lacked the experience for what was effectively a national vote.

The government's decision in August 2017 to direct the bureau to run the survey raised questions whether the agency, reeling from job cuts and trying to move on from the 2016 "censusfail" saga, was capable and resourced for the massive task at short notice.

Liberal senators on the inquiry committee submitted a dissenting report rejecting its findings, saying that past governments had given the bureau similar work.

The majority of the committee, investigating the arrangements for the survey, commended the ABS for its handling but said events leading up to the government decision to use the bureau for the task showed it was trying to conduct a public vote by other means.

"This was reflected in the terms of the directions given to the ABS, and placed the ABS in the difficult position of having to deliver what was functionally a national vote without any of the experience, practices or institutions that would ordinarily be available," the majority report said.

"Masking a vote as a survey devalues the ABS as an institution, and heightens the risks to the integrity of the process."

It recommended that human rights questions affecting minority groups should not be settled by public vote, and that the government consider more funding and support for mental health and LGBTIQ groups responding to consequences of the survey.

The inquiry report found the government was "unreasonable" to direct the bureau and other agencies to conduct the survey and deploy postal forms a month later, and that the ABS had to divert staff from other projects including the 2021 census.

In their dissenting report, Liberal senators James Paterson and David Fawcett said Labor and the Greens' decision to block a plebiscite led to the postal survey.

"It is therefore difficult to take seriously their protestations about the appropriateness of the mechanism," they said.

The ABS previously tested public opinion on nationally-significant policy questions, when the Whitlam government asked it to survey 60,000 people on their views about Australia's national anthem, the senators said.

A bureau spokeswoman said the postal survey matched the agency's purpose to inform important decisions by delivering statistics and data.

Bureau deputy Australian statistician Jonathan Palmer told the committee in an August public hearing that the ABS was up to the task and that the government had given adequate funding.

"The 2016 census online form outage did hurt the public reputation of the ABS. We acknowledge that. But we're seeing some rebuilding of that reputation following the release of a quality census data set," he said.

"I can assure you that we've reflected and learnt from the lessons of the 2016 census and we're applying those experiences and lessons to the conduct of this exercise.

"The ABS has been conducting large social surveys since the 1970s, and it's familiar with undertaking voluntary statistical surveys that seek views and opinions of Australians about issues such as their self-perceived wellbeing, social experiences and society in general."