Blyth Spartans said Graham Fenton has been "relieved of his managerial duties and placed on gardening leave".
In a statement, the club said they wanted to "express their gratitude for the work in which Graham has done at Croft Park since being appointed as first-team manager in August 2022".
The club are 14th in the table and won 3-1 at South Shields on Boxing Day, with some fans finding the move unusual given the mid-table position.
South Shields sacked Julio Arca after the defeat, with Josh Gowling also leaving Darlington after failing to turn things around since being appointed in September.
Blyth said Fenton had guided the club to preserve their National League North status during the 2022/23 season and has played an instrumental role in the development of the youth set-up via Tyne Metropolitan College too, taking full charge of the under-19s at the beginning of this current campaign.
The statement added: "From making 131 appearances and scoring 18 goals, having a brief spell as caretaker manager back in 2004, to being in charge for the past 16 months, his contributions across the whole club are hugely appreciated.
"In the interim, Jon Shaw will take full charge of the first-team. Further information and announcements will follow in due course."