The court document includes details of an incident in which Shigeta had allegedly taken a photo, during a 2004 ad shoot, of tennis player Maria Sharapova, which showed the tennis star with her legs propped up on the back of a director's chair unwittingly exposing her underwear. Biegel claims that Shigeta then passed the photos around to colleagues.
Another incident listed in the complaint involves a Czech brothel, which Beigel claims Shigeta tricked him and another colleague into visiting and encouraged them to sleep with a prostitute. Biegel said he refused.
He claims he complained to his employers that these incidents created a hostile working environment and that he was subsequently fired in November 2006.
Dentsu intends to sue Biegel for libel but is not denying all the allegations.
The company said in a statement: "When Dentsu refused to yield to Mr Biegel's unreasonable demands, he made outrageous allegations which the company has refuted.
"He has now filed a claim to obtain money, to which he is not entitled, for incidents he alleges took place over three years ago and which he never complained about while an employee of Dentsu.
"The company intends to counterclaim that Mr Biegel has libeled Dentsu and defrauded the company. We look forward to the opportunity to vindicate our company in court."
The Dentsu suit follows a similar case involving Julie Roehm, the former Wal-Mart marketing executive, who is suing the retail giant about her sacking, claiming that it breached her contract and smeared her in the press.
Wal-Mart has subsequently launched a counter claim alleging Roehm had an inappropriate relationship with a colleague, Sean Womack, the company's vice-president communications architecture. They have vehemently denied the allegations.