Rangers Supporters' Trust spokesman David Edgar said: "Let's not sugar-coat it, this was a disaster of a result. The fans are more upset than I can remember.
"The feel-good factor from Manchester (UEFA Cup final) has totally and utterly gone. It's hard to see where we go from here and it's down to the people in charge to show us.
"The fear is that players will be sold to balance the books and the fans simply will not stand for it. We are totally gutted."
Rangers Supporters Assembly president Jim Templeton labelled the side "a disgrace."
Templeton said Rangers owner Sir David Murray, boss Walter Smith and chief executive Martin Bain will see the fans frustration at a pre-arranged question-and-answer session at the club's training complex, Murray Park, on Friday.
He said: "You could call it a disaster but you could also say that the second-half display was a disgrace.
"They looked clueless against what was hardly a world-class team.
"The loss of money from going out of Europe is one thing but fans want to see what is on the park and the evidence of what we have seen tonight, there wasn't much.
"And if you are honest, there were signs of that at the end of the season.
"There is another couple of weeks before the transfer window closes and if ever there was evidence that we needed something, especially in the middle of the park, then tonight was it.
"There is a gaping hole there and it needs (to be) filled.
"Our AGM is this week and there will be fans coming from all over the world.
"There will be a question and answer session at Murray Park on Friday morning with Sir David Murray, Walter and Martin Bain.
That should be interesting."
Templeton insists Smith will survive the inevitable calls for his head.
He said: "It's a bit early for that.
"We are just looking for signs of progression but there hasn't been any."