The actor finished in fifth place in 2007's Any Dream Will Do, the BBC show which searched for a new star to play Joseph in Andrew Lloyd Webber's musical Joseph and the Amazing Technicolor Dreamcoat.
He has since embarked on a career on stage, and was set to play Prince Charming at the Alhambra Theatre in Dunfermline, Scotland.
However, he has now been replaced by CBBC's James Mackenzie after a member of the public spotted his porn background.
He has starred under the alias Ryan Ryder, with his own profile on the adult talent agency website JEM, reports The Sun.
A spokeswoman from the Alhambra Theatre said: "In light of information given by the public, of which we were completely unaware, we can confirm Craig Chalmers is no longer taking part in the pantomime."
Chalmers has stated that he is not "ashamed" of his new porn role, and explained that there had been a "crossover" period between his careers.
He said: "I'm not ashamed of it. I'm being well paid and I'm comfortable with doing it.
"The plan was to wrap my panto career up after this Christmas and concentrate on my new career.
"However there has been an unintended crossover and I'm well aware that there is a clear conflict of interest.
"I understand that a lot of people are going to judge me badly for it but at the end of the day both my friends and family are fully aware of my career and they support my decision."
Craig Chalmers has also previously performed with all-male strip group G-Force, while also being a member of boyband No Reason.
