CIA feared spy Down Under was passing on details of joint intelligence facility Australia's main intelligence agency was so deeply penetrated by a Soviet mole towards the end of the cold war that the US and Britain restricted the information they shared with Canberra, an investigation has claimed. The informer, a senior official in the Australian Security and Intelligence Organisation (Asio), leaked secrets to the KGB for at least 15 years but was never caught. A three-month investigation by the Australian Broadcasting Corporation (ABC) revealed that the CIA and MI5 feared the mole had been passing on information to the Soviet Union about Pine Gap, the top-secret intelligence facility near Alice Springs run by Australia and the US. Concerns about the informant first arose in the early 1980s, after the failure of a succession of Asio operations. Suspicion deepened in 1985 after a Soviet defector, Vitaly Yurchenko, gave some sketchy details about the traitor. Asio launched an intensive mole hunt known as Operation Jabaroo, working on the information from Mr Yurchenko and other vague details provided by US intelligence. 'We were aware of practically all steps taken or planned by Asio against Soviet targets in Australia,' former senior KGB officer Oleg Kalugin told ABC's Four Corners programme. Former general Kalugin said the Asio mole had first approached the Soviet embassy in the late 1970s, delivering a package of highly classified intelligence documents and promising more. The spy demanded payment of several thousand dollars per consignment. The Soviets were initially suspicious but their concerns were allayed after British spy Kim Philby, who had defected to Moscow, examined the documents and declared them genuine. The Asio mole and his handlers subsequently exchanged cash and documents through a series of hidden mailboxes known as dead letter drops. Asio launched an intensive mole hunt but failed to identify the source of the leaked information. A former secretary in the Australian attorney-general's department, Alan Rose, said that for a decade Washington had reduced to a trickle the amount of information it shared with Australia, starting in the mid-1980s. 'We weren't being taken fully into the Americans' confidence,' Mr Rose said. 'We weren't being trusted in a way which ought to exist between organisations with common goals. I think in hindsight it's pretty clear that for a period, the willingness to share high-grade intelligence had been largely withdrawn.' An intelligence expert from the Australian National University, Des Ball, told the ABC that any penetration of Pine Gap would have been disastrous for the US. 'A large part of the success with which it operates is dependent on the fact that those who it is targeted at know nothing about its technical capabilities,' Professor Ball said. 'A penetration would've been the worst thing the US intelligence community could imagine.' The search did result in the prosecution of George Sadil, a Russian language translator in Asio, who was convicted of improperly removing secret documents. But Australian intelligence officials believe the real mole was never uncovered, the ABC claimed.