A former ASIO spy is breaking a 46-year silence to reveal what she says is the darkest secret of all, something which the intelligence organisation and successive governments have never admitted in public.

“I have no doubt at all that ASIO was penetrated,” Molly Sasson told 7.30.

“The Soviets always seemed to be a step ahead of us. If we put on an operation, it failed.

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“There must have been a tip-off. It can’t have been otherwise.”

After working for British intelligence during World War II, and then MI5 in the post-war period, Ms Sasson was offered a job with ASIO in Canberra by its then chief, Charles Spry.

Molly Sasson had “one of the most sensitive jobs in ASIO”. Photo: ABC

Ms Sasson was given one of the most sensitive jobs in ASIO, to compile the daily intelligence report on Soviet diplomats who the agency suspected were operatives for the KGB or GRU, Soviet military intelligence.

“I used to get all the reports from the intercepts, from agents’ reports,” she said.

“I saw the static sight reports and had the surveillance team behind me and from that I got a pretty good idea of what they were doing.”

Former defence intelligence analyst Paul Monk backs Ms Sasson’s assessment.

“She was in pole position to learn what the organisation was learning and compare that to the follow-through on operations, which on her account went often astray or were aborted,” Mr Monk said.

At first, Ms Sasson put the failure of ASIO’s counter-espionage operations against the Soviets in Canberra down to incompetence.

But as operation after operation failed, she gradually came to a more sinister conclusion.

One operation in particular raised her suspicion.

She was chasing a suspected Russian agent who she believed was going to meet an Australian contact in a Canberra park.

“We were waiting for this particular man to come at 6:30 that night and they were all in place and I was in the office waiting,” she said.

“But they never turned up, he never turned up. He took the evening flight to Moscow.

“Then we found out that he had travelled from the embassy in the morning and drove to Sydney and caught that flight.

“So somebody tipped him off and he was keen to get out.”

Fears of Soviet mole inside ASIO dismissed

Ms Sasson was in no doubt that there was a Soviet mole working in ASIO.

She confided her fears to her immediate superior, ASIO deputy director Colin Brown, but those fears were dismissed.

“He said to me, ‘Well, don’t open this can of worms’,” she said.

Former defence intelligence analyst Paul Monk says the KGB identified Australia as a crucial target in the 1970s and 80s. Photo: ABC

In 1974, Ms Sasson also revealed her suspicions to Justice Hope during the royal commission into ASIO.

She was scheduled to have half an hour with Justice Hope, but ended up getting two hours.

There she handed over six sheets of evidence to him, which contained the names of several ASIO colleagues whom she suspected of being too close to the Soviets.

The royal commissioner reached no firm conclusion, finding only that “ASIO may or may not have been penetrated by a hostile intelligence service”.

Mr Monk said the KGB identified Australia as a crucial target in the 1970s and 1980s.

“It’s important to realise we’re a key part of an international security and intelligence network,” he said.

“The key players have always been the United States and Britain, but we’ve been closely linked into it since the beginning of the Cold War.

“What the Soviets set out to do was to get access to British and American intelligence, rather than simply ours, by the back door.

“And it’s been stated that they were so successful that they were getting access to everything via their assets in Canberra.”