The Prime Minister says a review of Stuart Nash's communications with donors found no additional instances of the former minister sharing confidential information.
One instance where Nash could have better managed a conflict of interest was identified, however.
In a statement provided on Friday, Nash said he hoped the report would "draw a line under this issue".
"It's thorough and does not identify any further instances in which I shared information with declared donors in a manner inconsistent with the Cabinet Manual," he said.
"I am now looking forward to building a post-political career and contributing to our wonderful country in other ways. I wish the Prime Minister and the Labour Party all the best in the upcoming election."
Nash was sacked from Cabinet in March after sending an email to two donors containing confidential Cabinet information. This was in breach of the rules for ministers and followed other issues with Nash's conduct.
Following the revelations, Prime Minister Chris Hipkins ordered a review by the Cabinet Secretary of Nash's correspondence with donors to understand if there had been any other breaches of Cabinet collective responsibility or confidentiality.
The report was released on Friday morning and Hipkins said no additional instances were found of Nash sharing information with donors in a way that breached the rules.
"When I asked for this review, I wanted to satisfy myself there were no other instances where confidential Cabinet information was shared with donors. I’m pleased that there were none," he said.
"Stuart Nash has already paid the ultimate price for his actions by being removed as a Minister. He is also retiring from politics at the upcoming election."
As Newshub revealed earlier on Friday morning, there was one instance identified of Nash identifying a conflict of interest in relation to the appointment of a close associate and donor to an advisory board. He took steps to manage this conflict, including removing himself from the appointment process.
The report found further steps could have been taken to manage the conflict, but that it is at the lower level in terms of inconsistency with the Cabinet Manual.
Hipkins said: "The report concludes he should have also declared his interest when Cabinet signed off the appointment and made it clear that another Minister was responsible but the review finds that this is at the lower end of transgressions and in fairness to Stuart he did take actions to manage the conflict. It's a helpful reminder of the importance of Ministers making sure their conflicts are fully managed."
Newshub understands a senior minister disputed whether the issue should be raised as part of the probe. The minister went into bat for Nash and say they understood there was a joint responsibility and the conflict was adequately managed.
Nash said on Friday that it had been the "ultimate privilege" serving under Dame Jacinda Ardern and Chris Hipkins. He said he was "very proud of the small role I have played in making New Zealand a better place for all".
"I always took my Ministerial roles and responsibilities very seriously and prided myself on being incredibly solution-focussed when faced with some of the most daunting issues any New Zealand government has ever had to deal with; from the 15th March terrorist attacks, to the White Island volcanic eruption, to dealing with Covid across my multiple portfolios.
"Serving the people of the Napier electorate and our wonderfully diverse communities has been my greatest pleasure. For a boy from the Bay to represent my home town around the Cabinet table and in parliament shows that, with a bit of hard work and tenacity, anything is possible."
He said he never shied away "from accepting responsibility for the actions that led to my Ministerial demise".
"I am now hopeful that the Cabinet Office report will draw a line under this issue."
Newshub has also seen documents showing the communications surrounding the immigration case Nash was accused of inappropriately involving himself in. When that came to light, the Prime Minister demoted Nash down the Cabinet rankings.
Nash called an MBIE official to advocate for a medical professional’s residence. The correspondence seen by Newshub shows repeated attempts to involve the associate Immigration Minister to no avail.
Nash resigned as Police Minister in March after admitting to once ringing the Police Commissioner to suggest he appeal a court judgement. That's a breach of the Cabinet Manual which says ministers shouldn't comment on or involve themselves in prosecutions or sentencing.
A day after Nash's resignation, it emerged that he had previously nearly faced a contempt charge after saying on radio that the killer of slain police officer Matthew Hunt should receive a lengthy sentence. The Solicitor-General ended up recommending the Attorney-General give Nash a telling-off.
The issues for Nash didn't end there though. The Prime Minister went on to demote Nash to the bottom of the Cabinet rankings and put him on a final warning after he found out that Nash had used inappropriate processes to advocate for a medical professional in an immigration case.
Nash's email to donors containing confidential Cabinet information came out at the end of March and led the Prime Minister to sack him.
Nash later confirmed he would stand down from politics at the October 14 election.
"There are many, many highs - and a couple of obvious lows - and I have made a number of life-long friends from both sides of the House as well as up and down this wonderful country," he said.
"I have had the privilege of serving in the Ardern Cabinet during the darkest of days, managing crisis after crisis after crisis, while driving forward an ambitious and progressive agenda of continuous economic and social improvement and transformation.
"While the work has been very rewarding, and both intellectually and professionally stimulating, it has also been incredibly taxing on relationships with family and friends. It's now time to address this balance."
