Trade Minister Tim Groser is refusing to sell shares he holds in a farming company that the Labour Party says leaves him open to accusations of a conflict of interest.
Mr Groser declared his retirement trust on the MPs Register of Pecuniary Interests but not the 40,000 shares it holds in New Zealand Farming Systems.
The company helps to develop dairy farms in Uruguay.
Under Cabinet Manual rules, he is required to declare only the trust.
Labour is calling on Mr Groser to sell the shares, but he says he has no intention of doing so.
Mr Groser says he will manage any potential conflict of interest.
He says he is unsure whether he can actively trade shares held in the trust.