The Portugal captain's future has been the subject of speculation in recent times, with reports claiming on Sunday that the Real Madrid forward would rather take a paycut to join the Red Devils than make the switch to Paris Saint-Germain.
However, the 28-year-old last month declared that he was happy at the Santiago Bernabeu, and Ferguson believes that the rumours could be the work of his agent.
"There hasn't been anything to encourage me to think Cristiano would come back here," Ferguson told the media. "As far as I am aware, there is nothing in it at all.
"Ronaldo has got two years left on his contract and it seems to me it is all part of the negotiations that are going on about a new deal.
"Maybe his agent is playing the game. I think it is false hope."
Ronaldo returns to Old Trafford in the Champions League on Tuesday.