The Republic of Ireland midfielder had looked set to follow defenders Wes Brown and John O'Shea from Old Trafford to the Stadium of Light, but the deal collapsed, leaving the 23-year-old's future uncertain.
And Ferguson believes the Black Cats may be stalling in order to force down the price.
"He was at the point of going to Sunderland and somewhere along the line, I don't know exactly when, I think Sunderland moved the goalposts," Ferguson told Sky Sports.
"I suppose their job is to try and save money. From what I can gather, they gave him an offer and then changed it. That annoyed Darren and I think he's quite right.
"If you can't trust them on day one why wait until day two?"
Gibson was omitted from the United squad for the club's pre-season tour of the USA, with Ferguson expecting the player to be on the move, but the United boss has now admitted he is unsure whether a deal will be completed.
"Darron was undecided about what to do when we made the group up to come here - and we both felt he'd be better staying back," Ferguson explained.
"He seems to be in limbo at the moment."
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