The Northern Irishman heavily criticised his squad after seeing the Bhoys slip to a 3-2 defeat to St Mirren in the Scottish League cup semi-final at Hampden Park
The Bhoys recovered from a 1-0 deficit to level things before the break but Charlie Mulgrew missed a second-half penalty as the Parkhead outfit slipped to a 3-2 defeat.
And Lennon was particularly critical of the spot-kick taker before roundly condemning a performance he described as "soulless".
He told reporters: “For some reason Charlie Mulgrew wants to side foot the penalty when I want him to put his laces through it.
“I am sick to death of us missing penalties, that was a game changer, but our reaction was poor from the second and third goals on.
"There was a lack of discipline in our shape, in our play, some of them behaved like spoilt kids out there. I’ve dealt with it in the dressing room and I’m not going to speak about it again.
“I am bitterly disappointed with that performance, it was soulless, it lacked intensity, it lacked desire, it lacked the will to win, it lacked all the attributes this team has shown over the last six to nine months.
“I don’t know where that performance came from, we didn’t start the game well, so we changed it after 10-15 minutes, we hit the bar twice, score a very good goal and looked a lot more like us.”
Celtic have now lost three games in a row at Hampden Park and Lennon admitted there may be a mental barrier his players need to overcome.
“It looks that way, because that was an impersonation of the team that I know, there’s no one player, with the exception of [Gary] Hooper who would get pass marks," he continued
"Defensively we were awful, I thought our decision making was poor, I thought going forward our quality in the final third was lacking.”
With the transfer window closing on Thursday, the former Leicester City midfielder also claimed he may look to make changes.
He added: “That was awful today from players I perceive to be top-class players, but maybe I’ve got it wrong and I need to look this week in the window and change things.”