"The directors believe they have done everything possible to back him during his period with the club but were left with not alternative but to terminate his contract with immediate effect.
"The club appreciates Mike Newell's efforts to take this football club forward and wish him all the best for the future.
"The club will now begin the task of selecting and appointing a new manager."
Youth team manager Neil Woods will take care of the side in a caretaker capacity.
Coca Cola League 2 Promotion 2009/10 Win Outright: Grimsby 100/1