The former New South Wales deputy privacy commissioner believes confidence in the 2016 census has been completely eroded and the results must be scrapped.

The Australian Bureau of Statistics (ABS) promised this year's census would be the "easiest and most accessible" ever, with the online form supposed to save time and money.

But a large-scale denial of service attack, combined with a hardware failure, forced the ABS to shut its website down and left Australians unable to complete the census online.

Director of privacy consulting firm Salinger Privacy and former NSW deputy privacy commissioner Anna Johnston called for a reset and rethinking of the entire process.

"I think they should scrap the 2016 census," she said.

"I think the quality of the data has been so compromised because of all the people who couldn't get through last night or got halfway through filling it in last night and it dropped out.

"They should scrap, start again and, when they're ready, run it in a way that better treads that fine line between protecting privacy and collecting good quality data.

"That means committing it to being — as it always has been — an anonymous national snapshot instead of a tool for detailed data linking on individuals."

'Senate inquiry needed' into how information is handled

Ms Johnston said there needed to be a Senate inquiry.

"In saying that the census should be scrapped for 2016, I’m not saying we try and repeat it again in six or 12 months," she said.

"I think there needs to be a Senate inquiry into how the ABS is going to handle privacy and information security moving forward.

"I think there should be proper national debate."

Ms Johnston said one of the problems with the changes the ABS introduced is that it was not a transparent process.

"They didn't explain to the people how they were going to use the census data and they did not limit themselves to how it might be used in the future."

Before last night the ABS said it had double the capacity it expected to need — the ability to handle 1 million form submissions every hour.

A former senior government official said:

"They painted a bloody great target on their foreheads. They asked for it."

What the ABS did not factor in was the hardware failure.

"They weren't able to meet the challenges that had been predicted — so I'm particularly concerned that that will equally translate into loss of confidence in how they're actually going to use our data," Ms Johnston said.