Parkinson was left furious on Saturday when referee Graham Salisbury opted to book winger Kyel Reid for diving after he went to ground under a challenge from Wolves goalkeeper Carl Ikeme during his side's 2-1 home defeat.
"Leading up to the game I did my homework on Wolves' penalties this season to let Jon (McLaughlin) know where their takers have been putting them," Parkinson said.
"(Wolves boss) Kenny (Jackett) won't have had to do that for us because we haven't had one.
"This is another example of where the decision hasn't gone for us. I don't agree with the decision the referee came up with.
"It was a very harsh decision not to get. Surely though, we are going to have to get a penalty decision go our way.
"Not to have one by this stage of the season, with all the attacking play we have created, all the attacking players we have and the amount of time we spend in the opposition's penalty area, is very frustrating.
"I could name a long list of incidents we've had this season where a penalty could have been given for us, so I'm getting frustrated by it all."