TORONTO -- A rare united front by three opposition leaders Tuesday wasn't enough to convince Premier Kathleen Wynne to agree to an independent review of Ontario's political fundraising rules.

Progressive Conservative Leader Patrick Brown, the NDP's Andrea Horwath and Mike Schreiner of the Green Party held a joint news conference asking for an open and transparent review process, and warning the Liberals not to change the fundraising rules on their own.

"One of the reasons that our initial meeting with the premier went so badly is the premise of our first request was that this be non-partisan," said Brown.

"It will lack legitimacy if she has it hijacked by the premier's office or dictated by the Liberal party."

Horwath agreed the Liberals should not be in charge of reforming the regulations around campaign financing.

"The rules that govern our democracy should be built fairly and they should be built to last, not made according to the whims of any one political party," she said.

Wynne said the Liberals will introduce legislation next month to ban corporate and union donations, lower maximum contribution limits and regulate third-party advertising, and will send the bill out for two rounds of public hearings.

She wants some of the changes in place by Jan. 1, and claimed the opposition demands for an independent review panel would only delay the needed reforms.

"I am not willing to delay the process, I'm not willing to slow it down," Wynne told the legislature.

"I'm not willing to buy into the stalling tactics of the opposition parties."

The opposition leaders want a panel with equal representation from the four parties as well as members of the public, labour, business and academia, which would hold public hearings before making recommendations on new fundraising rules.

And they say their process could be done just as quickly as the Liberals' public hearings on their legislation.

The Green party wants to get the influence of "big money out of politics," and said the Liberals should open up the review process and not act on their own.

"It needs broad public input, and not just in committee hearings where people are responding to legislation, but actually in drafting the legislation," said Schreiner.

Horwath said she was "very disappointed" in Wynne's position, and warned another Liberal government-controlled committee is not the proper way to change such a fundamental part of the democratic process.

"It's very clear that the Liberal majority on committee is often used to shut down ideas and opposition amendments," she said.

"We need something that is broad, that's open and that's transparent, and that is not managed by or controlled by or directed by the premier's office and the governing party."

The opposition can call witnesses at the public hearings into the government's bill reforming the fundraising rules, added Wynne.

"The opposition parties can call whomever they choose to come speak to the legislation," said Wynne. "That's the definition of the democratic process as it works in this legislature and this province."

Brown still wants a public inquiry into the fundraising quotas of up to $500,000 that were imposed on Liberal cabinet ministers. He accuses them of soliciting donations from companies looking to get government contracts.

"We still believe a separate discussion needs to take place on what has happened in terms of a full examination of (government) contracts and grants, a spotlight on the ethical questions that have been raised," he said.

The Liberals have cancelled all private fundraising dinners and receptions, and Wynne said cabinet ministers will no longer try to raise money from companies lobbying their ministry for business.