The Blues were denied a place in the final after Andres Iniesta scored a 93rd minute away equaliser for Barca, in the game that witnessed many refereeing controversies.
Barcelona's Eric Abidal was sent off for the slightest of contacts with Nicolas Anelka. Chelsea also had calls for three penalty-kicks waved away by Norwegian judge Tom Henning Ovrebo.
"Of course players make many mistakes, coaches make mistakes and referees can make mistakes. Okay, it happens and it's all in the game," Hiddink said.
"But when you see two, three or four situations waved away, then, yes, it is the worst I have seen."
Despite his anger, the Dutch tactician rejected any thoughts that there was any intention from the ref to knock his team out of the competition.
"Conspiracy is a very tough word and, if there is, you have to prove it," the former Real Madrid coach added.
"Obviously there is a lot written and said prior to this game. I can only mention what I see. I cannot say whether UEFA wouldn't like another English final."
By beating Chelsea, Barcelona will stage a Spanish-English Champions League final when they take on holders Manchester United in Rome on May 27th.
Robbed
Hiddink was successful in halting Europe's strongest attack for 160 minutes over two legs, and the Russia coach feels bitter that his team were robbed by Iniesta's killer strike.
"It is quite a disappointment that we did not finish it. We can be critical of that. But it was the overall feeling of being robbed, of an injustice.
"That it why it was so hot and angry in the dressing room. I could fully understand the feeling of the players."
Chelsea wasted a number of opportunities that could have put the result beyond doubt for the Londoners before Iniesta's late goal.