The commission says it reviewed 50 technical disclosure reports and found that 40 of them — or 80 per cent — had some form of non-compliance with the requirements.
And it says in a report that roughly 40 per cent had at least one major instance of non-compliance.
The new disclosure rules came into effect following a massive mining fraud at Bre-X in 1997, when the company's claim of a major gold discovery in Indonesia proved to be false.
The securities commission says companies that don't meet the requirements can expect staff to request a refilling or ask for additional disclosure.
The regulator also says it will continue to monitor technical reports filed by Ontario mining companies and will take appropriate regulatory action when the requirements aren't met.
"It is important that investors have accurate and meaningful information about material mineral properties in order to make informed investment decisions," Huston Loke, the regulator's director of corporate finance, said in a statement Thursday.