Labour's deputy leader Annette King questioned whether the Prime Minister was deliberately kept in the dark about Mike Sabin's plight in the lead up to the election as a political tactic.
Ms King, a former Police Minister, said it was standard for ministers to pass any sensitive information on to the Prime Minister.
If Mr Key was not told by his ministers, it was possibly for political purposes.
TVNZ has reported police started investigating Mr Sabin in August - about six weeks before the election. If the news had broken at that time it risked derailing National's campaign at a critical point. Ms King said she had regularly briefed former Prime Minister Helen Clark on sensitive matters.
"Prime Ministers do not like to be surprised by issues and information Ministers have, they like to know. Unless you want to go round saying 'I don't know anything about this" and you want to have deniability. Now that could be a political tactic this Prime Minister has, but I can assure you it wasn't the last Prime Minister."
Police Commissioner Mike Bush has also refused to confirm any briefing of ministers, but said that overall the Police had not dropped the ball on the 'no surprises' practice.
Mr Woodhouse said that was a general comment rather than confirmation of a briefing on the Mike Sabin case.
That requires Government departments to alert ministers of sensitive issues.
Labour's Andrew Little has claimed he believes the Prime Minister had known more than he was admitting to.
Ms King believed news of an investigation into Darren Hughes had leaked into the media as a result of Police briefing the minister so she had little doubt that Police briefings on such matters had continued under National.
Meanwhile, Prime Minister John Key says he stands by his decision not to stand former Mike Sabin down as a select committee chairman when he knew Mr Sabin was facing problems.
Labour leader Andrew Little yesterday stepped up his criticism of Mr Key for his handling of the matter, saying Mr Sabin had chaired a meeting of the law and order select committee just two days after Mr Key claimed he was told Mr Sabin had issues to deal with in December last year.
Mr Little said that showed a "cavalier attitude" towards Parliament given the law and order committee is charged with oversight of the police.
Mr Key said he had made a judgment call based on the information he had at the time and still believed it was the right decision. "I accept it was a judgment call, some people might criticise me for that. Things ... did progress and things did change. But on the information I had on December 1 I was happy with the decision I made."
He refused to say what information he had or whether his decision was influenced by assurances Mr Sabin had given about his situation. He said his chief of staff, Wayne Eagleson, had spoken to "a number of sources".
Mr Key's office has previously confirmed Mr Sabin told Mr Eagleson directly a day or two before Labour informed Mr Eagleson.
Mr Little said allowing Mr Sabin to chair the select committee while under investigation was a major conflict of interest.
Candidates
Labour's 2014 candidate Willow Jean Prime will contest the Northland seat again. Maungatoroto dairy farmer Grant McCallum, 50, says he will seek selection for National. He is considered the front runner. Others contesting it for National include Northland Federated Farmers' president Roger Ludbrook, farmer and private investigator Matt King and engineering company owner Ken Rintoul.
