Identified only as 'Alberto P.' the informant is aid to have worked for the German government's official press as a freelance sales representative in Central America and gave information both Schäuble and his state undersecretary Werner Gatzer, the news magazine said.
"As I've written to you in earlier mails, I have in my possession over 30,000 mails and documents in this case. You could contact me. The door to dialogue is always open. Please don't say in future that you didn't do anything because you didn't know what happened," he is reported to have written.
When the Panama Papers were exposed, it was discovered the law firm at the center of the story — Mossack Fonseca — had been used by the Federal Printing Office's then-director of international business, Jörg Baumgartl, to create a shell company in Panama, called Billingsley Global Corporation, to handle deals in Venezuela. The shell company was likely used to keep certain contracts secret, or may even have channeled money for bribery to secure contracts. Baumgartl denies all wrongdoing.
Alberto P. says that a lawyer on behalf of the Federal Printing Office wrote to him asking him not to send any more correspondence, which has been going on throughout 2012 and 2013.
The Finance Ministry denies any wrongdoing. In an emailed statement to broadcaster Deutsche Welle, the ministry said it was "inaccurate" to suggest that it had not heeded warnings.
"The company management and the supervisory board of the Bundesdruckerei has in the past few years carried out, or commissioned, several internal checks and compliance audits, as well as through an external law firm and an accountancy firm. The Ministry of Finance was closely involved," it said.