The inner workings of China's notorious secret police unit and how it hunts down dissidents living overseas – including in Australia – have been exposed by a former spy in a Four Corners investigation, raising tough questions about Australia's national security.

It is the first time anyone from the secret police – one of the most feared and powerful arms of China's intelligence apparatus – has ever spoken publicly.

The investigation also found the existence of an espionage operation on Australian soil only last year and the secret return of an Australian resident to China in 2019. Spy speaks out

The spy — who goes by the name Eric — worked as an undercover agent for a unit within China's federal police and security agency, the Ministry of Public Security (MPS) between 2008 and early 2023.

The unit is called the Political Security Protection Bureau, or the 1st Bureau. It is one of the Chinese Communist Party's (CCP) key tools of repression, operating across the globe to surveil, kidnap and silence critics of the party, particularly President Xi Jinping.

"It is the darkest department of the Chinese government," Eric said.

"When dealing with people who oppose the CCP, they can behave as if these people are not protected by the law. They can do whatever they want to them."

Four Corners has chosen not to publish Eric's full name or the identities of his secret police handlers due to concerns for the 39-year-old's safety.

Eric fled China and arrived in Australia last year where he revealed his history to ASIO, Australia's domestic spy agency.

ASIO declined to comment for this story.

Eric revealed to Four Corners how China collects intelligence on those it deems enemies of the state – and in some cases the tactics it uses to see them return to China to face prosecution.

He was tasked by his handlers with hunting down dissidents across the globe, sometimes by using elaborate cover stories — once as a property executive and another as an anti-CCP freedom fighter — to try to gain their confidence and lure them to countries where they could be abducted and returned to China.

Four Corners has seen hundreds of secret documents and correspondence that back up Eric's story about his assignments and targets which covered China, India, Cambodia, Thailand, Canada and Australia. 'Secret agents in Australia'

In 2023, AFP officers raided a Sydney location and uncovered a Chinese espionage operation targeting Australian residents.

One of them was Edwin Yin, a political activist whose online videos have targeted President Xi and his daughter.

The AFP spoke to Mr Yin after the raid.

"They told me ... they had disrupted an intelligence agency in Australia," he said.

"They acquired information and material that indicated the CCP was looking for me in Australia through this intelligence agency."

Four Corners understands the AFP's investigation is ongoing.

In 2021, Mr Yin was the victim of a physical attack in Melbourne that left him with a broken nose. Mr Yin thought the two men who attacked him, and a third who filmed it, were Chinese government agents.

"I don't feel safe in Australia," he said.

Eric was asked to target Mr Yin in 2018.

He told Four Corners he has no doubt Chinese secret agents currently operate in Australia, and that they rely on a network of support organisations and businesses.

"In an area where there are secret agents, a support system is required so when the agents are dispatched there, they can receive the necessary support," he said.

"They certainly have established a support system in Australia."

China says it is seeking Mr Yin's return over several financial fraud allegations. Four Corners spoke to one of his alleged victims who maintained the crimes happened.

Mr Yin says he was framed. China's global reach

Counter-intelligence experts said it was "political security" with which China's vast spying network was most concerned.

Holden Triplett previously led the FBI's office in Beijing where he regularly dealt with the Ministry of Public Security.

"The MPS portrays itself as a police service … but in my mind, they're anything but that," he said.

"Their job is to protect the party's status … and when I say status, I mean control … The party has to remain in control."

Under Mr Xi's rule, that control has become much tighter. Since becoming leader in 2012, Mr Xi has reordered the Chinese security and intelligence services and strengthened the party's grip on the Chinese population overseas.

"Now they're heavily engaged in the world, they need resources from all sorts of places," Mr Triplett said.

"So anyone within the Chinese population internally, or in the diaspora … that could threaten the party's control … that's what they would be investigating, opposing and disrupting if necessary."

MPS works with other elements of China's national state security including the country's foreign spy agency, the Ministry of State Security, and the CCP's main foreign influence arm, the United Front Work Department (UFWD).

The UFWD is tasked with increasing China's influence abroad and UFWD-associated community groups exist in virtually all countries where there is a significant Chinese population – including Australia.

"United Front work creates tall grass to hide the snakes," said former CIA analyst Peter Mattis.

"The MPS are some of those snakes." Citizens returned

Mr Xi has used his anti-corruption campaigns Fox Hunt and Sky Net to return more than 12,000 so-called fugitives to China since 2014. Many were returned in covert operations without the knowledge or permission of local authorities.

As part of Fox Hunt, in 2014 two Chinese police officers covertly entered Australia to pursue and return a Melbourne bus driver. When it was made public the following year, it caused a major diplomatic incident and the Chinese government promised it would never happen again.

In 2019, Chinese officers came to Australia again and returned with a 59-year-old Australian resident.

"The MPS sent officials … to Australia to have a so-called heart-to-heart with a female who was then persuaded to come back," said Laura Harth, campaigns director at human rights NGO, Safeguard Defenders.

"They used the [Australian] Chinese consulate-general and embassy to help them."

Four Corners has established that the AFP did approve the 2019 visit, but the Chinese officers didn't follow the agreed protocol and the woman was escorted back to China by them without the AFP's approval.

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Last month, Safeguard Defenders released a report documenting more than 280 cases of foreign citizens and residents being repatriated to China. The individuals are accused of committing economic crimes.

There were at least 16 successful individual extrajudicial returns from Australia between 2014 and 2023, according to the report, which relied on Chinese state media. Four of those returns took place last year.

"These successful operations — or even the attempts at operations that turn out not to be successful — are a clear violation of Australia's sovereignty," Ms Harth said.

A spokeswoman for the AFP said it "will never endorse or facilitate a foreign agency to come to Australia to intimidate or force foreign nationals to return home".

"Under Australian law, that is a crime," she said.

"It is an offence for foreign governments, or those acting on their behalf, to threaten culturally and linguistically diverse communities, or anyone else in Australia. This includes harassment, surveillance, intimidation and other coercive measures."

An Australian Government spokesperson said defending against malicious foreign interference was "a top priority".

"Australia's law enforcement and intelligence agencies assess, investigate, disrupt and where possible, prosecute acts of foreign interference."

"The ASIO and AFP-led Counter Foreign Interference Taskforce is actively investigating a range of foreign interference cases."

The Embassy of the People's Republic of China in Australia and China's Ministry of Foreign Affairs did not respond to a request for comment.