The Australian Electoral Commission has drastically increased its spending on external contractors, after using labour hire companies to boost back-end staff for the last federal election for the first time.
The commission has also repeated its warning that its funding in-between elections is too low, and posed an "ongoing risk" to its operations.
The federal agency used its 2018-19 annual report to sound the alarm about its funding levels, warning the current model posed a "significant risk" in managing increasingly complex federal and by-elections, as well as the growing electoral roll.
It has made similar warnings for the past two years.
While the commission secured extra funding for the six by-elections held last financial year, it won't actually receive the money until 2019-20, resulting in an operating loss.
"Funding received between elections for ongoing operations is also insufficient and restricts the AEC's ability to provide long-term election system sustainability or ongoing innovation," the commission said.
The Department of Finance has begun an overarching review of the commission's funding, which will be handed down in the next year.
But while the commission struggles with ongoing funding, its spending on external contractors has ballooned.
The commission paid external contractors around $81.4 million last financial year.
It was a big increase on the previous year - $18.4 million - because of the need to scale up for the May election.
More than 90,000 people were hired to help get Australia to the polls - up from around 75,000 the previous election.
However, the 2018-19 spend was more than double the bill for contractors during the year of the previous election.
In 2016-17, the commission spent $35.1 million on contractors.
An Australian Electoral Commission said the change came down to the way it sourced services for the 2019 election.
While the commission has used labour hire companies to employ polling officers for many years, it also used a panel of temp agencies to boost its office staff for the first time this year.
In previous years, the electoral commission hired staff through the traditional public service model. Using labour hire companies for surge staffing was "more flexible" than directly hiring, a spokesman said.
He also said it was simply a matter of moving money from one line area to another, as the spending money on contracted staff saved on wages and salaries. However spending on wages and salaries grew to $157 million last year - up from $128 million during the last election year.
A Community and Public Sector Union spokesperson expressed concern about the growing contractor spend.
"Proof continues to pile up that the arbitrary staff cap on the public service is causing cost blowouts and damaging vital services but the Morrison Government is still refusing to act," they said.
"The work done by the AEC is absolutely vital and must be done right. AEC staff, both permanent and casual, have important corporate knowledge and the last thing you want in that agency is labour hire, which brings with it job insecurity, reduced training and staff churn."