The highly secretive source behind the Panama Papers, the largest leak of confidential data ever analysed by journalists, has released a detailed manifesto explaining why he decided to blow the whistle.

Key points: Source says he has never worked for a government or intelligence agency

Source says he has never worked for a government or intelligence agency Reveals he is willing to work with law enforcement

Reveals he is willing to work with law enforcement Says Mossack Fonseca should pay for its "crimes"

Says Mossack Fonseca should pay for its "crimes" Describes papers as "glaring symptom of society's diseased, decaying moral fabric"

Speaking for the first time since leaking more than 11 million documents "John Doe", as the source is known, revealed he was willing to share the data with authorities.

"In the end, thousands of prosecutions could stem from the Panama Papers, if only law enforcement could access and evaluate the actual documents," he said in a four-page statement shared with the International Consortium of Investigative Journalists (ICIJ).

Hundreds of investigative reporters from news organisations around the world, including the ABC's Four Corners program, the BBC and the Guardian, worked in secret with the ICIJ for months analysing the unprecedented leak of 2.6 terabytes of internal data dating back to the 1970s, revealing the inner workings of law firm Mossack Fonseca.

The documents, which include internal emails, contracts, bank records and property deeds, revealed the Panamanian law firm had set up more than 200,000 shell companies, foundations and trusts in tax havens around the world.

John Doe pointed out while shell companies are not illegal by definition, they are often associated with the crime of tax evasion, and the Panama Papers reveal "they are used to carry out a wide array of serious crimes that go beyond evading taxes".

Despite pressure from authorities in several countries, all those involved in the ICIJ project vowed not to share the information with law enforcement, a decision John Doe endorsed.

"ICIJ and its partner publications have rightly stated that they will not provide them to law enforcement agencies" he said.

"I, however, would be willing to cooperate with law enforcement to the extent that I am able."

John Doe addresses speculation about identity

Previously German newspaper Suddeutsche Zeitung, which shared the data with the ICIJ, revealed it had taken extreme security precautions because it believed John Doe's life was at risk.

John Doe's statement responded to speculation about his identity.

"For the record, I do not work for any government or intelligence agency, directly or as a contractor, and I never have," he said.

"My viewpoint is entirely my own, as was my decision to share the documents with Suddeutsche Zeitung and the International Consortium of Investigative Journalists (ICIJ), not for any specific political purpose, but simply because I understood enough about their contents to realize the scale of the injustices they described."

The papers prompted demonstrations in Iceland and later forced the resignation of prime minister Sigmundur Gunnlaugsson. ( Reuters: Stigtryggur Johannsson )

The statement also outlined a frustration with the media, revealing some global media companies had been offered the material but declined.

John Doe said prior to Suddeutsche Zeitung, the media had "failed" to understand the true significance of the information he could provide.

"Despite explicit claims to the contrary, several major media outlets did have editors review documents from the Panama Papers. They chose not to cover them."

Media organisations, including the New York Times, have expressed frustration that they were not involved in the ICIJ's Panama Papers investigation.

"The sad truth is that among the most prominent and capable media organisations in the world, there was not a single one interested in reporting on the story. Even WikiLeaks didn't answer its tip line repeatedly."

Sorry, this video has expired Explainer: Panama Papers

In the statement, the source said he was encouraged that a global debate about tax reform had started, but authorities' lack of action was telling.

"For 50 years, executive, legislative, and judicial branches around the globe have utterly failed to address the metastasizing tax havens spotting Earth's surface," he said.

"I decided to expose Mossack Fonseca because I thought its founders, employees and clients should have to answer for their roles in these crimes, only some of which have come to light thus far.

"It will take years, possibly decades, for the full extent of the firm's sordid acts to become known."

Source wants protection for whistleblowers

John Doe also called for increased protection for whistleblowers, saying those who expose unquestionable wrongdoing deserve immunity from government retribution.

"Until governments codify legal protections for whistleblowers into law, enforcement agencies will simply have to depend on their own resources or ongoing global media coverage for documents," he said.

"In the face of political cowardice, it's tempting to yield to defeatism, to argue that the status quo remains fundamentally unchanged, while the Panama Papers are, if nothing else, a glaring symptom of our society's progressively diseased and decaying moral fabric," he said.

The Australian Tax Office said it was in possession of some of the data and was investigating more than 800 Australians named in the leak.

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