York have sacked manager Gary Mills following Saturday's 2-0 home defeat to Yorkshire rivals Bradford.
Mills, 51, who led the Minstermen back to the Football League last season via the Blue Square Premier Division play-offs, has departed the club after nearly two-and-a-half years in charge.
He also steered the club to victory in the FA Trophy final at Wembley last season, but York have failed to win any of their last 11 league games and have slipped to within four points of the relegation zone.
A statement released on the club's official website read: "It is with regret that the York City board of directors has terminated the contract of manager Gary Mills with immediate effect.
"The recent playing form, which has resulted in the team achieving only six points out of a possible 33, has led the board to this extremely difficult decision.
"The York City board of directors' absolute priority is to safeguard the club's Football League status and an improvement in results is essential due to our current league position.
"We would like to thank Gary Mills for his great contribution to York City Football Club and for managing last season's promotion team. We wish Gary the very best for his future career. The York City board hopes to make an announcement regarding the club's new manager within the next week."
Mills, a striker with Nottingham Forest, Notts County and Leicester during his playing days, managed non-league sides Grantham, King's Lynn and Tamworth before a brief spell as Notts County boss in 2004.
After a stint in charge of Alfreton he returned for a second spell at Tamworth and was then installed as Neil Redfearn's successor at Bootham Crescent in October 2010.
Mills steered York to a 2-0 FA Trophy final win over Newport at Wembley in May last year and followed that up eight days later by leading them back to the Football League for the first time in eight years after a 2-1 victory over Luton in the play-off final.