The photograph of Monaghan, a NSW and Australian representative, was taken during Canberra's Mad Monday festivities.
Monaghan issued a statement through his manager Jim Banaghan today expressing both remorse and disgust at an alcohol fuelled prank that led to images being circulated across social networks.
“Joel can’t blame anyone but himself for an act of stupidity that will haunt him for the rest of his life,” the statement said.
“Joel wants to make it clear that he was the one playing a prank on an absent team mate by simulating the act.
“There are no words of explanation that can be offered because none can be appropriate.
“Joel has to now face his family as well as fans and supporters with that shame and has already undergone counselling to help him cope with the consequences of what has happened.
“It was a moment of abject stupidity brought about by too much drink and a complete lack of any thought process.
“The fact that someone has sought to compound the situation further by the use of social media only adds to the trauma but Joel accepts that it is his actions alone that are at fault.
“He apologises unreservedly for the outrage that people feel at the moment and blames nobody but himself.
“He will meet the club over the issue and accepts that there must be ramifications but the fact is he is not in a fit emotional state to have those discussions at the moment.
“Joel is a genuinely good person who is simply shattered by a moment of sheer madness.”
Raiders CEO, Don Furner said he had not seen the picture but had been informed of its content and was investigating further.
"If he did it, it is something he will live with for the rest of his life," Furner told reporters in Canberra.
"We don't know whether it's authentic but I am as appalled as everyone else.
"If he did do it, I don't know why he would do it."
