Haslam, 39, resigned from his position with the Northern League club to join Chris Hardy and Lee Bullock in Whitby’s management team.
He has previously been head coach at Marske United, who he helped win the Northern League back in 2014, and Bishop Auckland.
Haslam said: “I’d like to go on record and thank the board of directors, the volunteers, the players and the amazing fans for their support during my time as manager of this great football club.
“I have met a lot of new friends and it is with a heavy heart I move on. It is progression on a personal level and I’m looking forward to the challenge that lies ahead.
“I wish everyone at and associated with the club nothing but the best moving forward.”
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