The striker claimed he was fit to play last season but was rarely selected by Lennon, and his temporary successor John Kennedy.
New Parkhead boss Ange Postecoglou has held discussions with the Scotland international and a new deal is expected soon, but Lennon has fired back at the forward and explained the background from his side of the dispute – including Griffiths’ lockdown conditioning and lack of training.
“He let himself down,” Lennon said. “We had worked really hard with him to get him back on track and before the lockdown, he was in the team, scoring goals, doing absolutely fine. Then he comes back completely out-of-condition, way, way behind any of the rest of them.
"For me, that was totally unacceptable.
“Leigh’s trying to make it out that it was alright and it’s not. He’s saying, ‘I’ll prove people wrong’ – but he hasn’t. He didn’t get picked for Scotland, you have to ask why.
“He’ll say he didn’t play enough games. Towards the end of the season I wasn’t there, John obviously felt he wasn’t in the right frame of mind or condition to play for Celtic which is a very high standard.
He added, on BBC Scotland’s Euros Breakfast Show, “The bottom line is, if I had a fit and hungry Leigh Griffiths last season, he would of played, because I signed him!”
Lennon also revealed the lengths the club went to during lockdown to keep players fit – but says Griffiths failed to take advantage of any of their Lennoxtown offering.
“We opened the training ground. You couldn’t come into the building but my fitness coach set up training for groups of two to train for an hour a day – fitness work, every day.
“Callum McGregor, Scott Brown, James Forrest, Greg Taylor, Jonny Hayes – all the lads that lived in Scotland came in. Leigh didn’t come in one day – not one day.”
Griffiths was frequently named amongst the substitutes and told Radio Scotland: “I said it towards the end of last season, if you’re fit enough to be on the bench then you’re fit enough to play games.”