Catherine Smith, assistant secretary, telecommunications and surveillance law branch at the AGD, told the Parliamentary Joint Committee on Intelligence and Security that it has not excluded any cost models but has come up with three possible models. This includes government pays; industry pays' and sharing the cost, which she said is the current arrangement.

Data retention:

"One of the biggest challenges for us in the early works that we did in 2009, 2010 is that it is very difficult ... to get any quantification of what this would actually cost because some providers gave us figures that were [high] and other providers gave figures right down [low]. I think that was a lot about not really understanding what it would look like at that time," Smith said.

"Essentially, we haven't done any actual cost modelling or anything like that at this point in time, but we're open to what potential [costs] there would be."

Committee member Philip Ruddock questioned whether imposing costs on the industry could drive some companies out of business.