US whistleblower Edward Snowden described the manifesto of the source of the Panama Papers leak as essential reading, ahead of the online release of more data expected Monday.
"The anonymous source of the #PanamaPapers speaks for the first time. Must read," Snowden wrote on Twitter late Friday, linking to the statement by the source identified as "John Doe."
Snowden, known for his revelations about the extent of surveillance by the US National Security Agency (NSA), is praised in the manifesto for "shining a light on obvious wrongdoing."
The International Consortium of Investigative Journalists (ICIJ) said it would release details of another 200,000 shell companies and clients of Panama-based law firm Mossack Fonseca on Monday.
Doe's anti-capitalist manifesto denounces global inequalities and charges the global financial system with fostering "economic slavery."
"Income inequality is one of the defining issues of our time," it begins, before moving on to accuse Mossack Fonseca of using its influence "to write and bend laws worldwide to favour the interests of criminals over a period of decades."
The unprecedented data leak details how money was funnelled to shell companies in tax havens and calls into question the finances of numerous politicians, sports stars and celebrities from over 80 countries.
"The Panama Papers show beyond a shadow of a doubt that although shell companies are not illegal by definition, they are used to carry out a wide array of serious crimes that go beyond evading taxes," the whistleblower wrote.
Doe, who says he works independently, called on the European Union, the United States and other governments "to take swift action not only to protect whistleblowers, but to put an end to the global abuse of corporate registers."