TORONTO -- Ontario's budget watchdog has agreed to investigate claims by the Progressive Conservative government about the size of the autism program budget.

The financial accountability office's probe was requested by a Liberal, with the party saying the Tories' numbers don't add up.

Children, Community and Social Services Minister Lisa MacLeod announced last month that in order to clear a waiting list of 23,000 children, all kids diagnosed as being on the autism spectrum would receive direct funding to pay for treatment.

On the day of the announcement, government officials said the new program would cost $321 million a year, as it did under the previous Liberal regime.

But since then, MacLeod has said the Liberals had budgeted $256 million for the program, and that when the Tories came to power last summer, she found the program was "broke."

MacLeod said she went to the Treasury Board to ask for an extra $100 million to keep it afloat.

Treasury Board President Peter Bethlenfalvy said in the legislature Wednesday that the Liberal budget for the program was $256 million. There was $62 million "in holdback," which was released by the Treasury Board, and MacLeod then asked for an additional $40 that was provided, he said.

Interim Liberal leader John Fraser said the previous government's budget was indeed $321 million for its autism program, with part of those funds held by the Treasury Board as is standard practice.

"There's a process at Treasury Board, which says we're going to give you this much right now, and you have to come back and tell us that you've done what you said you were going to do, and that you're able to use this other money that we're going to give you," he said. "It's a check and balance that has to be in government."

The financial accountability office said its investigation will take several months.

Meanwhile, the new program kicks in on April 1, and families say they are still lacking details of how it will work. A large protest is set to take place Thursday on the lawn of the legislature, but MacLeod said she will not attend because she has received threats.

"The tone of the debate has caused me some concern with my own personal security," she said. "We certainly respect people who want to protest peacefully."

Her office said the threats included ones on her life and came through social media and by phone to her constituency office. The threats have been reported to police, said spokesman Derek Rowland.

Parents are calling for autism funding to be based on children's individual needs, instead of just their age and family income.

Under the program, families will get up to $20,000 per year for treatment for children under six and $5,000 a year for children six to 18, but intensive therapy can cost up to $80,000 a year, and only families with an adjusted annual net family income of under $55,000 will be eligible for the maximum amounts.

The Liberal caucus is planning to attend the protest, in a reversal of the situation in 2016, when parents protested the Liberals' program and members of the then-Opposition Progressive Conservatives supported them.

Fraser said the Liberals heard parents concerns and ultimately made changes. He urged MacLeod to do the same.

An autism service provider, which received direct funding under the Liberal plan, said in a statement Tuesday that while it participated in consultations for the new plan, its advice was not heeded.

"We recommended that the government consider in its funding approach the importance of evidence-based autism services, the unique service needs of each child and the importance of considering complexity of need," Kinark Child and Family Services president Cathy Paul wrote.

"We believe the new program will have significant limitations in terms of its ability to support the best possible clinical outcomes for children and youth with ASD."