Turnbull made the statement while speaking to the radio host Alan Jones on Thursday morning. "My prediction is that there will be some very serious consequences to this," he added. (Full interview is embedded below.)
The census site went down on Tuesday night, is still down and there is no indication when it will be back online. IBM was awarded a contract for $9.6 million in 2014 to run the show. It has earned considerable flak over the debacle.
In response to questions from Jones, Turnbull said a denial of service attack — which is what is claimed to have precipitated the meltdown — had led to the shutdown of the site. He said there had been no intrusion by hackers.
He said the site should be back up later on Thursday, pointing out that he had conferred with the Australian Signals Directorate and his colleagues who had some involvement with the census.
Turnbull said the DoS attacks were predictable and should have been dealt with, adding that there issues for both IBM and the ABS to answer on this front.
"There is no doubt there were serious failures in the system's preparation" for the census, he said.
Turnbull added that his calm demeanour on the programme hid the fact that he was extremely angry about what had happened. He promised that an inquiry would be held to find out what exactly had happened.