The Australian Bureau of Statistics has blamed the media for the failure of its census hotline and blamed an overseas denial-of-service attack for the failure of its census website.

In a strongly worded submission to a Senate inquiry, the Bureau also attempts to deflect blame for the overwhelming of its website on to its contractor, IBM.

The submission says from early on, both its call centre and its automated paper-form request service received far more calls than expected, forcing it to implement a "call blocking" where calls were answered and callers asked to call back later.

It blames "unexpected and unprompted media and social media focus on potential of census fines", for which it hadn't planned because its usual strategy is not to mention fines before the census night. Also Australia Post delivered letters informing people of the hotline more quickly than it expected and its census advertising campaign was more effective than it expected.