The Privileges Committee has recommended former Cabinet Minister Michael Wood apologise to Parliament over his failure to properly declare shareholdings.
The committee has found he was neglectful in his "duties over a significant period of time", but his "shortcomings in this regard" were not enough to amount to contempt.
Wood resigned as a minister in June, and was referred to the committee - which makes rulings on alleged breaches of Parliament's rules - after repeated failures to properly declare or sell shares relating to his portfolios.
Wood remains as MP for Mount Roskill, and has said he intended to seek re-election in October.
In its ruling released on Wednesday afternoon, the committee recommended that he be required to apologise to the House, and that the Standing Orders Committee consider clarifying how interests in trusts should be dealt with.
"Mr Wood has now corrected his previous returns, and has expressed regret for his actions. He has apologised to the Registrar for his failure to declare his interests in AIA and Contact and his failure to correct previous returns sooner," the committee's report said.
"The reason he did not correct his omissions appears to be a lack of knowledge of the requirement to do so, and a failure to think about his responsibilities in this regard.
"Failing to uphold parliamentary responsibilities because of a lack of knowledge of them amounts to negligence in the parliamentary context. It is not, however, a contempt in the context of the requirements of Appendix B [of Parliament's Standing Orders]."
However, the report also said that if all members had handled their responsibilities in the same way, the register's purpose "could be significantly undermined".
It reiterated a 2008 statement by the Privileges Committee which said MPs "are obliged to turn their minds to the interests that they have. The onus is on members to recognise and declare relevant interests".
Wood made his apology on Wednesday afternoon.
"The report confirms that I should have declared the shares I personally owned in the 2017 to 2021 period and that I should have corrected the register of pecuniary interests after I did correctly declare them in in 2022 and 2023.
"I would now like to take the opportunity to unreservedly apologise to the House. As the committee notes, this was an error on my part and I deeply regret it. I've learned a clear lesson. In an intense and all-consuming job, I lost sight of the importance of these matters and I will prioritise complete compliance in this area as I continue my work in the Parliament."
He thanked the committee for its report - saying it made points that would be useful to all MPs - and thanked MPs from across the House who had supported him.
Not declaring trust's shares not in error - report
Unusually, the report also criticised registrar of pecuniary interests Sir Maarten Wevers - who conducted an earlier inquiry into Wood's actions - for criticising the now-former minister.
"The registrar's report contained comments passing judgement on Mr Wood's actions in critical terms. We consider that passing judgement on members' actions is a matter for this committee rather than for inquiries conducted by the registrar."
Wevers had said in his report that Wood's failure to "turn his mind to his interests as he should have" had "demonstrated a worrying and ongoing lack of awareness of the need to correct errors and omissions".
It also disagreed with one of the registrar's findings, that MPs "must, under certain circumstances, declare shareholdings held in trust", saying the Standing Orders did not technically require interests held in trust or by third parties unless the investment was in real property.
"Appendix B does not require members to declare the shareholdings of trusts in which they have an interest. Clause 5(1)(b) refers to the pecuniary interests of members, not other entities they have an interest in, and clause 5(2) states that a member does not have a beneficial interest in a company simply because they have an interest in another company or business entity that itself has an interest in it."
The Committee said Wood not declaring the interests held by the J M Fairey Trust, set up by his wife's grandfather, was therefore not a breach.
They recommended the Standing Orders Committee consider "clarifying how interests in trusts should be dealt with".
"Rules and forms are clear but both need change if Parliament intends that shares held by trusts should be covered," the report said.
The powerful Privileges Committee - of MPs from all parties - considers and reports on questions of privilege relating to Parliament and MPs, such as breaches of Parliament rules. Privileges are powers and immunities which ensure Parliament is independent of the Crown and the courts.