Australia's first online census has had a rocky start with some people experiencing website problems while the hotline has become overloaded with calls.

While more than 1.3 million have successfully completed the Australian Bureau of Statistics' online form on Tuesday, many have experienced website crashes or error messages and taken to social media to complain.

The ABS & Census websites are currently experiencing an outage. We're working to restore the service. We will keep you updated. Thank you.

— Census Australia (@ABSCensus) August 9, 2016

One Facebook user said "is it just me or is the census offline?" while others vented their frustration using the hashtag #Censusfail on Facebook and Twitter.

"The #census2016 site is down. A quick census of the people in my house revealed no one was surprised to hear this," Facebook user Tom Taylor said.

The ABS has responded by advising callers to wait until Wednesday to contact the hotline "when (they) expect calls to reduce", assuring people they will not be fined if they do not complete their census on Tuesday night.

.@SmartState1 says the #censusfail calls into question the competence of @ABSCensus https://t.co/r9LjH79sgg #census https://t.co/VDRnSQhu41

— Sky News Australia (@SkyNewsAust) August 9, 2016

The 2016 census has been fraught with contention after it was discovered the ABS would be holding onto personal data for four years instead of the standard 18 months.

However, the ABS has promised private information will not be released.

The promise has come after several senators, including independents Nick Xenophon and Jacqui Lambie and Greens Scott Ludlam and Sarah Hanson-Young, vowed to risk the $180-a-day fine by withholding their names and addresses amid privacy concerns.

#ThisIsAustralia Imagine how much faster Census 2021 is going to be with copper #NBN #CensusFail #fraudband #auspol pic.twitter.com/B8OtYNeEWG

— Andrew Heslop (@AndrewHeslop) August 9, 2016

Former NSW deputy privacy commissioner Anna Johnston is refusing to fill in the census at all, despite census head Duncan Young repeatedly promising that everyone's data will remain top secret.

"Hand on heart, the security set-up in order for people to submit their information - it's encrypted all the way through from their browsers into the ABS's internal environment," he said.

"Then we go through the process of separation. The information is isolated so people who can access names can't access the rest."

About 24 million people from 10 million households are expected to complete the compulsory survey.