Labour leader David Cunliffe belatedly revealed an interest in an investment trust last year after initial legal advice that he did not need to disclose the financial interest.
Cunliffe on Tuesday referred to Investment Custodial Services Ltd (ICSL) which he described as a bare trust, alongside the Bozzie Trust which holds his family home
He joined ICSL in March 2012 but did not disclose it in the Pecuniary Interests Register in early 2013 - a record of MPs' interests that are worth more than $500.
However, after discussion with the registrar, who advised him "if in doubt declare it", he included the entry in a supplementary amendment in July 2013.
He is one of more than 16,000 investors with money in ICSL.
A number of MPs filed supplementary amendments to the register including Energy Minister Simon Bridges, Primary Industries Minister Nathan Guy and former Labour leader David Shearer.
A spokesman for Cunliffe said the amount in the trust was much less than $100,000.
Cunliffe earlier this week admitted a lapse of judgement, and apologised to his caucus colleagues, after confirming anonymous donations to his leadership campaign were funnelled through a trust.
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