The Shareholders' Association says it's disappointed that the NZX's new diversity reporting rule is limited to gender and won't make it mandatory for companies to have a diversity policy.
The NZX is introducing a new rule that means listed companies will have to disclose to investors how many women they have on their boards and senior management, but they don't have to have a diversity policy unless they want to.
But the Shareholders' Association says the rules do not go far enough in addressing the over-representation of middle aged white men on boards.
One of its board members Gayatri Jaduram says the policies should also cover age, education, ethnicity and other factors.
She says white middle class males are over-represented and they often have similar thinking.
Ms Jaduram says all sorts of people are needed on boards because having predominantly one type of person does not promote a diversity of thought.
NZX chief executive Tim Bennett says research shows diversity among senior executives is important in driving business performance, but he won't make it mandatory.
He says NZX can't force companies to do things, it can only put issues on the agenda.
"To try and mandate a full diversity policy for all of our listed companies, I think will get to the wrong result".
Mr Bennett says more importantly NZX is putting the whole diversity policy on the agenda for listed companies which will cause their boards to think about what's appropriate for their company.