Alexander has been in charge at Sincil Bank for four years

Speculation had increased that Alexander would leave the club after four years in charge following the Imps' play-off loss against Grimsby.

First team coach John Schofield will take temporary charge of the club with immediate effect.

Chairman Steff Wright told the club's website: "Keith has been an outstanding manager for Lincoln City and has helped lay the foundations for the future."

He added: "This board has been fully supportive of Keith and, although we are reluctant to part company with him, we wish him well with his future career."

Alexander, 49, led the club to four successive League two play-off campaigns since returning to Sincil Bank in 2002.