The alleged misconduct was reported to the corporate regulator by Cleveland managing director David Mendelawitz, who said he travelled with the executives and witnessed the drugging, Fairfax reports.
"It was amateur hour. We were trying to represent Macquarie to our partners in South America as the best and brightest, but they kept behaving like complete d**kheads. I was naive, and I certainly wouldn't accept this kind of behaviour now," Mr Mendelawitz said.
"It was malicious. Everyone was having a few drinks. They were certainly trying to cut him out of the picture and discredit him in front of me."
Fairfax reports the victim was removed from the Cleveland account in July 2011 after a discussion with Macquarie's HR department, and no action was taken against Mr Rosenbaum or Mr Whiting.
The victim is seeking compensation for loss of income and medical costs.
A Macquarie spokeswoman said in a statement: "Macquarie treats any allegations regarding inappropriate or potentially illegal behaviour with the utmost seriousness, regardless of their source. Where matters are raised, Macquarie conducts a thorough investigation and where appropriate, notifies relevant authorities."
In a second statement released on Thursday morning, the company said: "Macquarie notes a Sydney Morning Herald/Age story published today and is surprised these publications have aligned themselves with a law firm seeking to solicit clients for a class action that has not even commenced.
"As this matter is the subject of threatened litigation we are yet to have the opportunity to put forward our account. The employees referred to in the article no longer work for Macquarie. Macquarie always encourages any client with a genuine concern to contact it directly. Macquarie has over 14,000 employees worldwide and demands the highest standards from them."
