Australian comedian Tom Ballard has strongly denied indecently assaulting an aspiring comedian four years ago after the alleged victim published allegations on social media.

The ABC host said the allegation was "extremely difficult" to address but was necessary, given the claim has made its way into the public domain.

The allegation was published on Facebook on Saturday, with the man alleging Ballard indecently assaulted him in a hotel room in June 2014. The man said he went to the police but they couldn't investigate further because Ballard "hadn't gone outside of the confines of the law".

The Tonightly host said in the statement he has been aware of the allegation for about six months.

"I have become aware of a claim being made about me," Ballard wrote on his website. "It involves an allegation of sexual assault: an allegation that I completely deny in the strongest terms possible. It fundamentally goes against who I am as a person and everything I believe in.