The Hawks are currently just six in the Championship division one table despite a decent start to the season.
Hallas, a former Great Britain international, decided he had taken Hunslet as far as he could, saying, “I accept full responsibility for the underachievement of the team and its players.”
Hunslet chief excecutive officer Alan Stephenson said, “Graeme has acted with great professionalism and dignity. He took over in difficult circumstances.”
Reserve coach Gary Lord will take over as head coach until a successor can be found.