The “true cost” of a plebiscite on same-sex marriage may be more than triple the federal government’s estimate of $160m, partly because of mental health harms to lesbian, gay, bisexual, transgender and intersex Australians, a report says.

Professional services firm PricewaterhouseCoopers calculated the real cost of the plebiscite at $525m, based on its estimates of $281m for the time cost of voting, $158m to conduct voting, $66m for campaigning and $20m for mental health harms to 50,000 LGBTI Australians.

Alternatives to a stand-alone plebiscite were less costly. A plebiscite held at the same time as a general election was estimated to cost $113m and a parliamentary vote without a plebiscite was costed at just $17m.

This suggests $508m could be saved if the plebiscite were rejected in favour of a parliamentary vote.

Luke Sayers, the chief executive of PwC Australia, said the findings showed a stand-alone plebiscite on marriage equality was a “massive waste of time and money”.

Sayers said a parliamentary vote was the best mechanism for change to minimise the cost to the economy and health and wellbeing of the community.

The Australian Marriage Equality national director, Rodney Croome, said the more information there was about the plebiscite, the clearer it became that it was an “incredibly costly and harmful opinion poll”.

“Every single government minister must read this report before cabinet considers legislation for a plebiscite,” Croome said.

“With the stakes so high for the economy and for the mental health of LGBTI Australians the government needs to reconsider its position.



“The best way to resolve the marriage equality issue is with a free vote in the parliament as soon as possible.”

The $20m mental health cost included an estimate of $4m for increased visits to doctors and psychologists. The report estimated 50,000 people – 5% of gay, lesbian and bisexual Australians – would seek treatment for anxiety or affective disorders as a result of divisive public debate.

The PwC report noted LGBTI Australians suffered higher levels of psychological distress and would be further harmed by a “high profile, national, public debate that will likely extend over a number of months”.

A PwC partner, Suzi Russell-Gilford, said arguments opposing marriage equality in the media and community forums would have an impact on mood disorders and mental health of LGBTI people. “This will be devastating for a segment of the community already more susceptible to mental health issues as a result of discrimination,” she said.

Russell-Gilford told Guardian Australia the estimates of increased health costs were conservative. In Ireland LGBTI mental health services reported the demand on their services doubled because of the same-sex marriage referendum last year.

The report noted the possibility that people with strong views against marriage equality might also experience mental harm but did not attribute a cost to this, citing an academic paper that found “no evidence” that marriage equality harms opposite-sex marriage.

The remaining $16m of estimated mental health cost was based on estimates of 50,000 LGBTI Australians taking one sick day each on average, and experiencing four days at half their usual productivity because of mental health issues.

In September depression and mental illness charity Beyondblue made a statement in favour of marriage equality, citing discrimination as a cause of increased anxiety and depression in LGBTI people.

PwC estimated the largest cost was $281m for the one hour it would take 15.5m Australians to vote on a Saturday or 30 minutes to submit a postal vote.

The $66m campaigning cost was based on an estimated $3.41 a voter of spending by the yes and no camps. This was an average of the cost of six similar campaigns, including Australia’s republic referendum and same-sex marriage referendums in 2008 in California and 2015 in Ireland.

A PwC economics and policy partner, Jeremy Thorpe, said “overseas examples show that spending on the ‘for’ and ‘against’ campaigns alone can reach over $6 per voter, as happened in California”. Campaign costs could increase further depending on whether and how much public money the government gave to each side.

The federal government has not yet made an announcement on public funding for the plebiscite campaigns.