Concern over former Australian jihadists: Attorney-General Senator George Brandis (right) and Director-General of Security, David Irvine. Credit:Alex Ellinghausen He also admitted that ASIO could not say for certain how many Australians were involved, saying ‘‘there could well be people of whom we do not have great visibility or any visibility at all’’. The tens of people who’ve returned were ‘‘self-identified’’, he said. ‘‘You would expect that we would be concerned about their activities on returning to Australia,’’ he said, though he declined to go into further detail. He also revealed there were ‘‘another 150 that we’re looking at here in Australia who have inclinations to support those ... extremist groups’’ – referring to the al-Qaeda offshoots the Islamic State of Iraq and the Levant, and Jabhat al-Nusra.

The legislation the government introduced on Wednesday will expand ASIO’s powers to conduct computer surveillance and make it easier to swap information with the foreign intelligence agency ASIS – seen as a useful tool against terrorism. The legislation has left out for now so-called ‘‘data retention’’, which would compel phone and internet companies to store ‘‘metadata’’ such as times, addresses and lengths of phone calls, text messages, emails and Skype calls – though not the content – for up to two years. The records would be kept by the companies, not the government, but authorities could later access that data for investigations and prosecutions – prompting privacy advocates to condemn it as an expansion of state powers. Senator Brandis said data retention was ‘‘under active consideration’’ by the government. On Thursday, Senator Brandis said the onus would be on government to ensure any data retention would not be arbitrary or unlawful. ''As I say, the government has not made a decision on that issue yet, but you’re also right when you say that western governments are moving in that direction,'' he told ABC radio.

''If this government were to make that decision then it would absolutely need to be hedged by safeguards. That’s what the bi-partisan parliamentary committee recommended.'' Senator Brandis said he was a ''liberal. I am against big government ''. ''I have a bred in the bones suspicion of big government and arbitrary power. So I, of all people, am going to ensure that whatever reforms in order to underwrite public safety are assayed in this area will be subject to appropriate safeguards.'' Senator Brandis echoed Mr Irvine's concerns about returned jihadists, pointing to the convictions of returned jihadists from Afghanistan a decade ago. ''A decade or so ago during the Afghan conflict, about 30 Australians travelled to Afghanistan to link up with the Taliban and engage in jihadist war fighting on behalf of the Taliban. Of those 30, 25 returned to Australia,'' he told ABC radio.

''Of those 25, 19 were involved in preparing and planning mass casualty terrorist attacks in Australian and of those 19, eight were actually prosecuted and convicted. So there is a very high incidence of returning jihadists to engage in counter-terrorism. ''As Mr Irvine has said on the public record, there have been four mass casualty attacks on the Australian homeland interdicted in the last decade or so. This is not a fanciful notion.'' Mr Irvine said on Wednesday that data retention was ‘‘absolutely crucial’’ because almost every ASIO investigation and most police investigations depended on such metadata. The second tranche of new counter-terrorism laws will likely be introduced to Parliament in spring, Senator Brandis said. Loading

He said the government would abandon its previous decision to scrap the key role of the Independent National Security Legislation Monitor, whose recommendations over the past two years form the basis of much of the government’s current review of counter-terrorism laws. Senator Brandis said that scrapping the monitor had been an ‘‘economy measure’’ and ‘‘not something we particularly wanted to do’’.