Under the code name "Peter Bernstein", Holger Friedrich reported on fellow soldiers during military service for the National People's Army.
Germany's Berliner Zeitung newspaper is to investigate its new owner after he confirmed reports that he had been an informant for the East German secret police, editors revealed in an editorial.
Holger Friedrich and his wife, Silke, bought the Berliner Verlag, the publisher of the Berliner Zeitung and the Berliner Kurier titles in September.
On Friday, Welt am Sonntag published documents showing Friedrich had been an informant for the East German Ministry for State Security, known as the Stasi.
Under the code name "Peter Bernstein", Friedrich reported on fellow soldiers during military service for the National People's Army.
The Stasi relied on an enormous number of informants — it is estimated nearly 2% of the East German population collaborated with the organisation — and maintained files on nearly six million of the country's 16-18 million inhabitants.
Friedrich has not denied the claims but told Welt he had been forced to collaborate after a failed attempted to flee the country and that he had taken every opportunity to avoid working for the Stasi.
In a joint editorial, the editors of the centre-left Berliner Zeitung and tabloid Berliner Kurier, respectively Jochen Arntz and Elmar Jehn, said they would investigate the matter "journalistically".
"We will collect facts, we want to see the files — the victims, and the perpetrator's file," they wrote, adding that they will work with experts for context and try to get in touch with some of the people mentioned in Friedrich's Stasi reports.
Their investigation will also focus on "why Holder Friedrich did not inform them earlier" of his connection with the East German secret police to uncover his "motivation".
They argue that their journalism on the matter will remain "clear and independent" and that it will be embedded into a wider debate about the divides still existing in the country 30 years after the fall of the Berlin Wall and what should and should not be forgiven.
Friedrich said the journalists will have his "full support and cooperation".
Berliner Zeitung was established in 1945 in East Germany and is the only paper from the former German Democratic Republic to have achieved national prominence since reunification.