However, the Conservative Party's former chairman Brian Dobbs said at the time that Mr Stringer had already been suspended from the party and was no longer a board member.
That meant the interim board and any decisions it made were illegitimate.
Mr Stringer said he still believed the board was legitimate and that Mr Craig was no longer a member.
But he had decided to step down to move the focus away from "Colin vs John" and to allow the party to consider its future.
In his resignation letter, he said: "I wish to take the heat and focus away from the personalities. I have never wished this to be a confrontation between Colin and myself, but unfortunately, that is what it has become."
The party's membership has not recognised Mr Stringer's interim board and is expected to elect a new board in the next few months.
Mr Craig is not seeking a position on the board, but has not ruled out re-running for the leader's role in the future.
At a press conference last month, Mr Craig admitted inappropriate conduct with former press secretary Rachael MacGregor, but rejected claims of sexual harassment.
The details of his interactions with Ms MacGregor are suppressed by a confidentiality agreement signed after a Human Rights Commission mediation.