A possible accounting change that could increase the size of Ontario's already record deficit isn't likely to take effect this year, Finance Minister Dwight Duncan said Tuesday.

In his annual report, Ontario's auditor general questioned the government's policy of excluding the $11-billion, unfunded liability at the Workplace Safety and Insurance Board from its own financial accounts.

Auditor Jim McCarter said that if the WSIB's debt was included in the province's books, the $24.7 billion-deficit would increase by 10 per cent.

Duncan said the choice to force the liability into the province's books was up to the auditor, adding that while McCarter signalled it was something he was considering, no decision had been made.

"If anything, it would move forward into next year but you'd have to ask him about how he intends to proceed," said Duncan, adding the change wouldn't be reflected in Ontario's current deficit projections because "it's too late in the year."

The WSIB, which collects premiums from employers and provides benefits to injured workers, said in August that it had posted a $3.34-billion loss last year as it took in $2.4 billion less than it paid out in benefits and other expenses.

The board's unfunded liability -- the amount by which its liabilities exceed its assets -- also rose to $11.4 billion last year from $8 billion in 2007.

In his report Monday, McCarter said that while the WSIB was treated as a trust, the latest figures raised concerns about whether it should remain one.

"Because trusts are supposed to have enough assets to cover their liabilities, they are exempt from being included on the province's books under accounting rules," McCarter said.

"But the WSIB does not have enough assets to cover its unfunded liability, and that unfunded liability is large and growing."

Progressive Conservative Leader Tim Hudak has been taking aim at alleged expense account abuses by the WSIB chair Steve Mahoney for months, saying the former Liberal cabinet minister is paid $550 a day for the part-time job, and billed taxpayers $141,000 last year.

He said that regardless of how the unfunded liability is accounted for, the bigger concern is why that amount grew so much in a year.

"However you treat the WSIB unfunded liability, you need to be transparent for taxpayers," said Hudak.

"But the bottom line here is that under Liberal friend and former MPP Steve Mahoney, we have seen the unfunded liability nearly double."

Mahoney has defended his $140,000 in per diems and said his $25,000 in 2008 expenses were all pre-approved and not out of line given all the travel he does for the WSIB.