The director of Australia's Security and Intelligence Agency (ASIO David Irvine and the deputy commissioner of the Australian Federal Police (AFP) Andrew Colvin have appeared at a joint press conference at which they explained the nation's new metadata retention regime is about consistency of and not a grab for new powers or to collect extra information.

The pair said the problem they face is that metadata is a very useful investigative tool, but that voice and data providers aren't compelled to record it or to use a particular format when they do. The government's intention to make collection compulsory, they explained, is nothing more than an effort to ensure that all voice and data carriers retain metadata.

“Some companies make sound commercial decisions for their interest not to store metadata,” Colvin explained. ASIO and the AFP would prefer universal capture and storage of metadata.

Colvin said at least one high-profile case, the murder of Melbourne woman Jill Meagher, was solved because the perpetrator's carrier is one of a handful that does store metadata. The lack of metadata, he said, is occasionally becoming an issue.

Irvine and Colvin were also at pains to point out that the proposed regime won't mean data on the web sites Australians visit will be accessible without a warrant. But both stopped short of saying IP addresses of websites citizens visit won't be recorded.

Colvin offered an example of the AFP obtaining intelligence that an Australian IP address visited an offensive web site. Under those circumstances, Colvin said, the AFP could execute a search warrant among Australian ISPs to determine if that IP address was used by one of their subscribers. If that search proved positive, the AFP could conduct a warrantless search to retrieve metadata associated with that IP address. To actually examine the content the user of that IP address accessed would then require a warrant.

Several questions attempted to establish just what internet service providers and voice carriers will be required to store in order to make such warrants useful.

The thrust of those questions appeared to be that metadata that records only a user's IP address, and not IP addresses of the sites a user visits, proves nothing and that surely ISPs will therefore be required to store records of sites a user access.

Colvin and Irvine were not, in your correspondent's opinion, able to explain that adequately, repeatedly stating that they cannot access any data that describes content. But of course if they've been told by a third party that an Australian visits a certain IP address, finding out what content resides there is a trivial task.

Earlier today, Communications Minister Malcolm Turnbull also tried to explain the government's intentions. In this radio interview he also ruled out retention of data describing website a user visits. ®