The visitors had Victor Wanyama dismissed for what appeared to be no more than a foul on Paul McGowan - who then netted a late penalty after Esmael Goncalves hit the deck at the edge of the Celtic box.
St Mirren also felt they should have been awarded a spot-kick in the opening half when the ball appeared to strike Georgios Samaras on the arm, but Lennon feels referee Bobby Madden got that call wrong as well.
"That was the most appalling refereeing performance I have seen for a long, long time," Lennon said. "I mean, you can't get so many big decisions so wrong, it is incredible.
"For me St Mirren should have had a penalty, it is a clear handball. You don't get many more as clean-cut as that so we dodged a bullet there.
"Then I see (Beram) Kayal getting wrestled into the advertising hoardings right in front of the linesman and he doesn't give a free-kick and two seconds later, I've got a man sent-off for nothing and the penalty that St Mirren did get was outside the box and there is no contact.
"So I am delighted that we got a point out of it but there is no doubt that the referee's decisions ruined what could have been potentially a good game.
"The sending off is ridiculous and it changed the game. I am concerned now about the standard of refereeing.
"I have kept my counsel on it for a couple of months but there have been some really bizarre decisions, not just against my team, which have baffled me.
"Today is by far the most blatant performance I have seen. It was really poor."