Australia's top spy agency ASIO still cannot be certain when it will move into its imposing new headquarters, despite former prime minister Kevin Rudd opening the building in July.


The $630 million building, which looks over Canberra's Lake Burley Griffin, was initially due to be ready for its top secret occupants in April last year, but the project ran into delays and budget overruns and is still waiting for its new tenants.


ASIO director-general David Irvine said while the building was ''substantially completed'', builders were still making sure all systems were working.


''I still cannot give you a date when the certificate for completion will be completed,'' Mr Irvine told a Senate estimates hearing, adding he hoped the building would be finished by the end of the year. ''In the best of all possible worlds, we will begin to move into the new building in the new year.''


The building has been the subject of controversy, with an ABC report that Chinese hackers had gained access to the blueprints. But Mr Irvine on Monday said there were no security problems.


AAP