Marine AFC have announced that manager Tommy Lawson informed the chairman that he has decided to step down with immediate effect.
Assistant manager Ian Johnson will take over team selection on a caretaker basis until a permanent successor is appointed.
The chairman, Paul Leary, has said he would like to thank Lawson for the contribution he has made over the last two seasons, especially to the FA Trophy run that the club enjoyed last season.
The run culminated in the trip to Dover Athletic. The club wish him and coach Dom Finnigan every success in their future roles.