She said she had a great meeting with Wynne on Monday, and her proposal for a public inquiry was an option Wynne should consider.
"I don’t think it's necessarily productive to have that highly charged, quite ugly political conversation gumming up the legislature. I think that putting it off to a third-party process, where there's open public hearings … is actually a good option," Horwath told CBC Radio's Metro Morning.
"The people of the province deserve some answers on this issue. We either get at those answers through the legislative process, or we get at those answers through a different process that opens up space in the legislature for us to deal with some of the other pressing issues that Ontarians are facing," she said.
Final price tag must be known, Horwath says
Horwath said it will be up to Wynne to decide which is the better way to deal with the issue, but she hoped Wynne understands that people deserve answers.
"We need to know who made those decisions, how they were made and exactly what the price tag was," she said.
Later Tuesday, Wynne told a news conference she wanted talk to Horwath about her proposal, but she hinted that it's not a priority for a government facing a deficit of $11.9 billion.
"I want to have that conversation with her. I want to find out exactly whether it is that thing she is looking for, or whether there is another way of getting at the information that she's looking at," Wynne said.
"I think we have to be very careful that we don't spend public dollars in a way that's not effective," she said.
On other issues, such as jobs, health care, home care and long-term care, Horwath said there is a lot of room for collaboration with Wynne, and she is prepared to work with her on it.
"I'll be bringing her some specifics within the next couple of days. I hope she'll work with me to achieve them," she said.
"If there are things that she brings to the table as premier that I am not supportive of, then I am not going to be supporting those things."