An accounting change has added nearly $22 million to the amount the Province of Manitoba expects it will have to pay to clean up contaminated sites.

When the Progressive Conservatives came into office, the province had an estimated environmental liability of $281 million. That number had not been adjusted for inflation since new public accounting rules were adopted in 2005-06, Pallister said.

In a 2012 report to the legislature, the auditor general recommended "the province revalue its environmental liabilities each year to reflect known changes in the liability including the impact of the passage of time, interest rates and an appropriate margin of error."​

The province didn't revalue all of its environmental liabilities until the 2017-18 year, a spokesperson for the office of the auditor general said.

"It truly underestimated the amount of liability on the part of these brownfield land sites," said Finance Minister Scott Fielding.

"A liability for the remediation of contaminated land really must be accounted for. Environmental standards exist and for far too long the province underestimated this."

To account for inflation, the province has added $21.8 million to its estimated costs for contaminated sites in accounts for the 2017-2018 fiscal year.

Pallister called the discrepancy an example of "stealth accounting, designed to mislead, designed to create a false impression."

The province announced the adjustment as part of a review of public accounts in an attempt to correct what it called a pattern of underreporting liabilities and overstating assets.

The province also announced Wednesday it was writing off $82 million for the second phase of the Investors Group Field Stadium loan, and $30 million in interest-free loans given to social services agencies that the province said it had little hope of collecting.

The loans will be reclassified as grants.