Former USMNT coach Jurgen Klinsmann has launched a scathing attack on Hertha Berlin's leadership in a revealing leaked diary of his ill-fated 76-day tenure at the Bundesliga club.

Published by German outlet Sport Bild on Wednesday, Klinsmann accused the club of a "culture of lying" and said its leadership were incompetent.

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Klinsmann's management has confirmed the authenticity of the document to German news agencies DPA and SID. They added they do not know who leaked the diary.

Earlier this month, Klinsmann resigned from his role, leaving Hertha shocked by his decision.

In the leaked 22-page diary, written during his time in Berlin, Klinsmann said: "The leadership must immediately be sacked. Should this not happen, all the good signings will turn into average players because there is one basic rule in football: You are only as good as the environment you play in."

The document alleges that issues at the club began once Klinsmann was appointed to the supervisory board and before being named interim coach.

On Nov. 25 the document said: "Klinsmann calls Ralf Rangnick, who has twice shown at Hoffenheim and Leipzig that he can do such jobs successfully. Rangnick makes it clear that he believes the project in Berlin is exciting but he would never join with [sporting executive] Michael Preetz."

On Nov. 29, just days after his appointment as head coach, Klinsmann wrote: "The planning for the winter preparation for the second half of the season for which Michael Preetz is responsible is a catastrophe.

"The club is in a relegation battle but they are planning like they are an international top club with numerous top players."

In response to the claims, Hertha released a statement to members, claiming the ex-Bayern Munich boss "deceived" the club. They allege he is attempting to "justify his resignation with absurd allegations."

Speaking at a news conference on Wednesday, Preetz said: "We took note of our former coach's allegations with deep concern.

"The club takes damage through things like that. We reserve the right to take legal action."

Klinsmann depicts president Werner Gegenbauer as an "ill-tempered" person who does not stick to his word and claimed director Preetz's relationship with the team was shaped by a "culture of lying which destroyed the mutual trust with the players."

He added that Preetz's reign, which started in 2009 has led to "catastrophic failings in the sporting department."

"The club would have been directly relegated to the second tier without the change in the dugout in November," the diary concludes following Klinsmann's resignation.

"They were just not prepared for this situation. Years and years of catastrophic failings from Michael Preetz in all things related to the sporting sector. Catastrophic squad planning by Michael Preetz.

"There is a culture of lying which destroyed the mutual trust between Michael Preetz and the players."

In further jibes at the club's media department and medical staff, Klinsmann said that sponsorship deals with Amazon and TESLA were tied to his name as well as a further €150 million cash injection by investor Lars Windhorst.

Hertha spent around €80m on new players in the January transfer window -- more than any other club in Europe -- but with 11 matches left to be played in the 2019-20 season, they remain in a battle against relegation.

Interim coach Alexander Nouri remains in charge ahead of Friday's trip to Dusseldorf, who are six points behind Hertha in the relegation playoff place.

Klinsmann, 55, was appointed by Hertha on Nov. 26, 2019, and won just three of his 10 matches in charge, losing four and drawing three.