Neil Lennon has insisted he did everything possible to turn Celtic’s season around.
He has resigned as manager with the club 18 points adrift in the Premiership.
Celtic had been chasing a historic tenth consecutive league title, but have struggled to find consistent form all season.
Lennon won five trophies in his second spell as Celtic manager after taking over from Brendan Rodgers in February 2019.
The Northern Irishman said he had “worked as hard as ever” to improve the club’s fortunes.
He said: “We have experienced a difficult season due to so many factors and, of course, it is very frustrating and disappointing that we have not been able to hit the same heights as we did previously.
“I have worked as hard as ever to try and turn things around, but unfortunately we have not managed to get the kind of run going that we have needed.
“I have always given my best to the club and have been proud to deliver silverware to the Celtic supporters. The club will always be part of me. I will always be a Celtic supporter myself and I will always want the best for Celtic.
“I would like to thank so many people at the club who have given me so much and I would also like to thank my family for their love and support. I wish the Celtic supporters, players, staff and directors nothing but success for the future.”