Tony Docherty reckons the penalty awarded against Dundee in their defeat to Celtic was "soft".
The Dens Park side lost 3-0 to the Scottish champions after a David Turnbull spot-kick was followed up by goals from Kyogo Furuhashi and Matt O'Riley.
Ryan Howley challenged Turnbull on the edge of the box and a penalty was given after VAR intervened following referee Grant Irvine’s free-kick award for the original foul.
And Docherty feels the decision was harsh, stating there was "minimal contact".
Speaking to Sky Sports, he said: "I was really pleased as we executed a game plan that we have been working on all week and I thought we done it really well.
"You know when you are playing at Celtic Park, there are no congratulations at half time. It is so important in that opening 10-minute period in the second half, I have seen them do it so many times [score].
"I am really disappointed with the penalty. It is such a soft penalty to concede and when you lose the first goal, that is the most important thing.
"To lose it in that manner... I think David Turnbull is very cute as there is minimal contact. I have watched it back a couple of times and the referee gives the decision as being outside the box and to go back and look at it again was very harsh on us.
"The game plan never changed from the first half to the second half. You know Celtic are going to come out with that impetus to try and get the game won early.
"My intention was to try and hold things until the 60th minute and then bring on substitutes to bolster things upfront so there are loads of things for me to be pleased about in terms of the players carrying out a plan."
