The government is required by law to issue a report each year on the $4.4 billion dollars it spends on the plans, but the most recent one available on the ministry's website is from 2007-2008.
Tory Frank Klees cornered Health Minister Deb Matthews during question period, asking why the government hasn't done its job and made the information public.
"She doesn't even know that that report has been missing for five years," Klees said in the legislature. "That's why our health-care system is in the mess that it's in."
Matthews didn't answer Klees' question in the legislature, but told reporters later that she didn't know that the reports hadn't been tabled for five years.
"I am going to get to the bottom of it," she said.
A 26-page report covering the years 2008 to 2012 was tabled a few hours later in the legislature and was later posted on the health ministry's website.
But Klees said the missing reports are yet another example of the lack of oversight by the governing Liberals, who are already feeling the heat over diluted chemotherapy drugs and the fiascos at Ontario's Ornge air ambulance service and the eHealth electronic medical records agency.
"For the minister to be staring back across the way like a deer in headlights, not knowing what I'm talking about when I asked this question? Something's wrong here," he said.
If the Ministry of Health and Long-Term Care was a corporation, the CEO would be fired, he said.
"There is a vacuum of leadership here and there's an incompetence on the part of the leaders," Klees said.
The reports allowed the public to see what prescription drugs are covered by the province, how much money the government spends in different programs, and other indicators, said NDP health critic France Gelinas.
There's a "culture of secrecy" in Ontario's health-care system that's protecting the government, not the public, she said.
"The core mandate of the Ministry of Health is to oversee the health-care system," Gelinas said.
"Right now, they are failing in their core mandate on many, many fronts."
Zita Astravas, a spokeswoman for Matthews, said the money spent on the Ontario Drug Benefit Program — accounting for about 10 per cent of the total health-care budget — is published annually in the government's financial statements.
According to the ministry, the ODBP was established in 2007 to make funding decisions, negotiate agreements with drug manufacturers and determine which drugs should be covered by the province.
Ontario's publicly funded drug programs — including those for seniors and welfare recipients — account for nearly 43 per cent of spending on prescription drugs in the province, it said.