The body overseeing the census has admitted shutting down the online national survey will cost taxpayers up to $30 million.
The Australian Bureau of Statistics told a Senate estimates hearing on Wednesday night the 40-hour outage means the expected $100 million saving from moving the census online was now more likely to be about $70 million.
"We have to date probably incurred additional costs of around $20 million ... and we anticipate possibly spending another $10 million," chief statistician David Kalisch said.
Government frontbencher Zed Seselja admitted errors were clearly made but insisted many lessons had been learnt.
"The prime minister has made it very, very clear that it's unacceptable," he told reporters in Canberra.
"I'm sure the ABS has learnt its lesson."
Former cabinet minister Eric Abetz said many millions of Australians were inconvenienced by the "debacle".
"I think responsibility needs to be taken," he told reporters.
"But by whom and in what form, that is to be determined by those that are in charge."
