"On the face of it, he's made a mistake, but until we know the details, it's premature to make that call [to resign]," he said.
The petition follows Tania Billingsley's call for Mr McCully to resign for his "really incompetent handling of the situation".
Muhammad Rizalman bin Ismail, a former defence attache assistant at the Malaysian High Commission, is accused of burglary and assaulting Ms Billingsley with intent to rape. He was arrested on May 9 but invoked diplomatic immunity and returned to Malaysia on May 22.
The New Zealand Government said it had always wanted Rizalman to stand trial in New Zealand, but an ambiguous communication from an official led to a belief that the Government was happy for Rizalman to return to Malaysia.
Labour's foreign affairs spokesman David Shearer stopped short of saying Mr McCully's head should roll.
"The honourable thing for him to have done was to say, 'My ministry failed, and I failed to follow up, and I'm prepared to offer my resignation'."
He and the Green Party want the review of the ministry's handling of the case to be external and independent. Greens co-leader Metiria Turei called for Mr McCully to stand down for the duration of the review, which should include the actions of ministers.
A spokesperson for Mr McCully, who is on his way to Europe, said the minister had nothing to add to his previous statement. That did not address Ms Billingsley's specific request for his resignation, but said he had publicly apologised to her and is awaiting the result of a fully inquiry.
Meanwhile, NZ Law Society president Chris Moore said media coverage of the case "may be coming close to harmful interference with the process of how we determine guilt".
Auckland University law professor Warren Brookbanks said: "The the defendant could be prejudged in the court of public opinion when he has no opportunity to answer or offer a defence to the allegations."
He said the all the publicity meant "there will be real problems in getting an impartial jury".
"In going public in this way the complainant risks jeopardising her credibility as a witness, potentially weakening the prosecution case."