Smalling has now said sorry for what he admitted was an "insensitive decision".
The photograph taken of Smalling in his fancy dress appeared on the front page of The Sun newspaper on Thursday and immediately prompted his management company to release a hasty statement.
The company said the photo of Smalling was taken at a private party at his home.
He is shown in the snap with what looks like a mock circuit board and mobile phone around his chest, and cables leading up his body.
Also on his body are bottles of Jagermeister and cans of Red Bull, while he is also wearing an Arab keffiyeh head dress.
Smalling's management company have claimed that it was an elaborate pun on the popular 'Jagerbomb' which is a mix of the two drinks.
"Chris and his girlfriend hosted a fancy dress party to celebrate Christmas and their belated birthdays with close friends in the assumed privacy of his own home," Wasserman Media Group said in a statement.
"He dressed in a costume consisting of empty bottles of Jagermesiter and cans of Red Bull strapped to his chest in an attempted comedy play on the popular 'Jagerbomb drink'.
"Although he fully accepts in hindsight it was an ill-thought out and insensitive decision, absolutely no harm was intended whatsoever and he apologises for any offence caused."
United have declined to comment on the issue.
- Chris Smalling