The Hoops held top spot for a large portion of this campaign but a couple of poor results in recent weeks have let Old Firm derby rivals Rangers back in.
‘Gers now sit four points clear at the top ahead of Celtic’s trip to Heart of Midlothian tonight and Lennon admits it will a great opportunity lost if the Bhoys fail come season’s end.
"It's easy to make excuses, but if you don't win the league then you have to look closer to home - and we will,” he said.
"We've had a foot in the front door and it's closed again. But it's not over yet.
"Our priority was to win the league and it still is.
"It would be a major disappointment to me and to the club if we don't.
"We feel we've played very, very well this season and been very consistent.
"And if we don't win the league we will have to look back and say we haven't done enough in some areas in some games.
"We will just have to look to redress that next season."