The Cameroonian joined Rangers on transfer deadline day in August, with Joey Barton heading to Marseille for a season-long loan as part of the deal.
Mbia tweeted Barton about swapping clubs on Monday, but the 26-year-old is adamant that he did not have control of his account.
"I do not know how this happened. Someone must have got hold of my login and password because I did not write these things," Mbia told The Guardian.
"This was not me. I did not write the tweets, and I have made people at the club aware of that. I saw the messages this morning and spoke with the club about them, but now I see there are more appearing in my name."
QPR head of media and communications Ian Taylor said: "The club is aware of tweets from the official twitter account of #QPR midfielder Stephane Mbia today.
"Stephane Mbia has informed the club he is not responsible for these tweets. The club will continue to investigate and deal with the issue internally."
Mbia spent three years at Marseille.