TORONTO -- Ontario's government spending watchdog says there are too many uncertainties for it to determine the financial impact of the Liberal government's cap-and-trade program to fight climate change.

The financial accountability office says it's too early to say if the provincial government can raise the $1.9 billion it expects each year from auctioning pollution emission credits to industries, even though cap-and-trade begins Jan 1, 2017.

It says the impact on the province's deficit will depend on how many emission credits are sold, at what prices and what the U.S. exchange will be on the auction revenues.

However, the opposition parties say the report shows the government can use cap-and-trade revenues on previously announced programs to "artificially" balance the books next year as promised.

Progressive Conservative finance critic Vic Fedeli says cap-and-trade amounts to a "cash-grab" by the Liberals, and will let them book revenue now and pay expenses later so they can eliminate the $4.3 million deficit.

NDP environment critic Peter Tabuns says the financial accountability office report shows the government can "play games with the cap-and-trade money" to make their books look good at the expense of the climate crisis.

"The big one really for me is the government can take the money, make their books look good, and not actually take on climate change," said Tabuns.