Thousands of Australians have queued outside Centrelink offices as the online portal for government services crashed while people scrambled to apply for benefits amid the coronavirus pandemic.
Government Services Minister Stuart Robert backtracked on his earlier claims hackers were responsible for crashing the MyGov website.
Mr Robert said the site could only handle 55,000 users at one time, telling parliament on Monday the site had 95,000 visitors.
This triggered a distributed denial of service alarm as the system thought it was under attack.
"The DDoS alarms show no evidence of a specific attack today," Mr Robert said.
Mr Robert said that didn't mean there was no need for tighter cyber security.
"MyGov has not been offline, it's simply suffered from a distributed denial of service attack this morning," he said earlier in Canberra.
Former Labor leader and government services spokesman Bill Shorten said Mr Robert lied "to cover his own behind".
"He's the one who should be queuing up at Centrelink," he wrote on Twitter.
The Australian Cyber Security Centre is investigating.
"At this stage, the ACSC has no evidence to suggest this outage was caused by malicious cyber activity," a spokesperson said.
Australian Council of Social Service chief executive Cassandra Goldie said everyone was under a lot of pressure as they faced unemployment.
"The most important thing is to try and keep attempting to get online," Ms Goldie said in Sydney on Monday.
Mr Robert has urged people to go online to put in their claims.
Centrelink will boost its workforce by 5000 people to deal with the influx of applicants and extend call centre hours.
But there will be fewer staff in offices because of social distancing requirements and no pop-up shopfronts are planned.
Many families, workers and business owners have been forced to seek social security payments as the pandemic throws the national economy into chaos.
Nigel Phair from the UNSW Canberra Cyber centre said there had been no indication it was a malicious attack.
"Considering the amount of workers who are now displaced from their job and needing to apply for benefits, it would be quite easy to overwhelm the Centrelink website and call centre operations," he told AAP.
"When you add many people have more than one device (desktop, laptop, tablet, phone) and use each to try and apply, then this traffic flow is exacerbated."
Mr Shorten said the unprecedented demand was "entirely foreseeable".
"But at this hour of need, Australians are having to grapple with inadequate service, online glitches and a lack of planning to deal with demand at Centrelink shopfronts," he said.
Right across the country, long queues of people snaked around blocks outside Centrelink offices.
First-time welfare recipients have been told they can only get a customer reference number by applying in person.
Mr Shorten said the minister must do better.
Australian Associated Press