WikiLeaks founder Julian Assange requires WikiLeaks staff to sign a confidentiality agreement that claims the organization's collection of leaked documents is "solely the property of WikiLeaks," according to a published report.

The confidentiality agreement says that unpublished documents leaked to the organization are "valuable proprietary commercial information, the misuse or unauthorized disclosure of which would be likely to cause us considerable damage."

The legal agreement was leaked to the New Statesman and published Wednesday [PDF].

Clause 5 of the confidentiality agreement imposes a penalty of 12 million British pounds, nearly $20 million, on anyone who breaches this legal gag, claiming the extraordinary penalty is based on "a typical open market valuation."

New Statesman's David Allen Green said the confidentiality agreement was a sign that WikiLeaks perceived itself as a commercial organization that intends to make a profit off the materials others leak to it.

"One suspects that the various brave and well-intentioned people who have provided the leaked information would be quite unaware of – and perhaps horrified by – the express commercial intentions of WikiLeaks, as evidenced by this document," he noted.

Assange had previously threatened to sue the British newspaper The Guardian if it published stories based on documents leaked to WikiLeaks before he gave his permission.

He later threatened to sue the newspaper again after it published a book about its collaboration with him. Assange said the book contained "malicious libels," apparently because it noted he initially refused to remove the names of informants mentioned in Afghan war documents.

"The irony of an organization dedicated to the free and open flow of information threatening to sue a newspaper will be lost on no one," a spokeswoman for The Guardian said.