NZX rejects claims that it should carry out spot checks of the financial accounts of listed companies.
The Shareholders Association claims an analysis of 47 publicly-listed companies indicated 20 of them are at risk of defaulting on their loans.
Chairman Bruce Sheppard says stock market operator should be more vigilant as the recession puts companies under more pressure.
Mr Sheppard says the NZX should do this work - not him - and it is not doing its job.
But NZX says it does not have a mandate to scrutinise company books.
It says companies are required to inform the market of important information that may affect its business. Any breaches can result in both criminal and civil action.
It also argues there is a robust process in place to ensure companies are complying - including following up on unexpected trading of shares or large price movements, as well as checking out market rumours or complaints.
NZX says the Securities Commission can also investigate companies separately if it sees fit.
