After Ardern reviewed email correspondence from a complainant on Wednesday that showed how harmful the process had been for the complainants, she challenged Haworth and Haworth resigned.
The following day the ex-staffer, who had agreed to work away from the parliamentary premises since media reports first surfaced about the complaints five weeks ago, also resigned.
In a statement, he said the situation was stressful and he did not want to distract from the work of the Government.
The Herald understands the ex-staffer's employment contract would have included a "relationship breakdown" clause that could have been triggered by either the ex-staffer or the Labour leader, given that he worked in the Labour leader's office.
That role was about meeting the needs of MPs for the daily running of Parliament and was based in Bowen House, not on the ninth floor of the Beehive, where Ardern's office is.
Invoking the breakdown clause could have led to a payout of three months' salary.
It is likely the clause was being looked at when Ardern told reporters on Wednesday that she was seeking advice on the ex-staffer's employment.
But Ardern would not confirm that when asked today by media this afternoon.
Asked if she had considered invoking the clause for safety reasons, she avoided the question.
"Obviously you'll be aware that the employee in question ... has not been present in the precinct for roughly five weeks.
"Obviously yesterday I received that resignation and I won't be saying any more than that."
She declined to comment on whether there was any pressure on the ex-staffer to resign.
Stuff reported that the draft terms of reference for the QC review may only look into the alleged sexual assault and bullying, not the party's process in dealing with them.
But Ardern said the terms of reference would meet the needs of the complainants, who have said the process had been unfair.
"I have an expectation that there are questions to answer around the process, so that does have to be looked into."
She said it was now her job to make the Labour Party a safe environment as well as a place where people with complaints can come forward comfortably.
National Party deputy leader Paula Bennett has claimed that many advisers and colleagues close to Ardern were told about the sexual assault claim, but Ardern said she was comfortable with how her staff had handled the matter.
Yesterday Ardern said the Labour party's senior vice president, Tracey McLellan, had temporarily taken the position of acting party president, in accordance with party rules.
But the party's general secretary, Andre Anderson, told the Herald today that there was nothing in the party's constitution about an acting president, and no one was in that role.
He said McLellan and Maori senior vice president Tane Phillips had taken on more responsibilities, but kept the same positions.
Ardern said today that when the position was vacated, the rules defaulted to the senior vice president.
The party president role is expected to be filled during the Labour Party annual conference in late November/early December.
