The comment came in response to Shiels's claims that the Celtic boss was "paranoid" for complaining about the lack of Hoops players on the PFA Scotland Player of the Year shortlist.
Lennon described the absence of his players from the shortlist as "abysmal" last week, prompting Shiels to say: "Celtic make a song and dance about everything, don't they? Paranoid FC."
Speaking after Celtic's 3-1 defeat at Motherwell, Lennon continued the feud by likening Shiels to Brent - a vain, deluded and self-promoting office manager from the BBC series, The Office.
"Kenny has always had plenty to say about our club," said Lennon. "He likes to ramble on in little monologues, he is a bit like David Brent sometimes. He is an unconscious comedian.
"Nothing surprises me from Kenny. He has had a couple of barbed comments about my team and the club over the last couple of years so he must have a personal agenda, I don't know, you would need to ask him about that.
"I do take exception to the paranoia [comment]. That's been thrown at our club for the last 15 to 20 years but I think the last three or four years have proved that we weren't paranoid, we were just right."
Michael Higdon, who was among the nominated players on the list, scored a penalty for Motherwell in Sunday's game at Fir Park.