The Financial Markets Authority says there are many easy steps companies can take to improve the quality of information disclosed to investors.
The FMA has published a survey of the level of disclosure by 45 listed and unlisted companies of information about how they are run.
It said listed companies publish more than unlisted companies, but both types should be talking about issues such as codes of ethics, remuneration policy, and risk management.
FMA director of strategy and risk Simone Robbers said companies - big or small, listed or unlisted - could take note.
"Take a stocktake. What are you already pushing out, is it useful, canvas some of your stakeholders - are they actually reading it," she said.
Meanwhile, the guidelines to finance sector companies on the standards of behaviour expected of them which the FMA released last week, have been described by a lawyer as fuzzy and without proper statutory foundations.
The FMA's code said finance, investment and banking companies' conduct should put the interests of customers first, although it stressed they were guidelines only.
But Chapman Tripp partner Ross Pennington said the guidelines had no clear relevant statutory basis and were open to subjective interpretation.
He called the guidelines "fuzzy law", saying they were vulnerable to swings in the mood of the FMA similar to the Australian Securities and Investments Commission's recent crackdown on banks over alleged misconduct.
Mr Pennington said the guide was also at odds with government policy which, in another financial sector review, rejected making fair treatment of customers a statutory duty.
However, he said despite the guide's shortcomings, companies and senior executives would do well to study it.