TORONTO -- Ontario's auditor general is stepping up her fight with the Liberals over government advertising, warning proposed changes would undermine her independent office and could lead to the public paying for partisan advertising.

Auditor General Bonnie Lysyk said the changes would make a "mockery" of an independent office of the legislature. The proposed changes to legislation would reduce her office to rubber stamping government ads, she said, even ones she feels are partisan.

"The changes that are being proposed would enable advertisements to be put out there that could be deemed partisan," Lysyk said.

"To me it seems odd that something so important as this Government Advertising Act...changes to it that are very significant are embedded in a budget bill."

Lysyk was the one who wanted the act opened up in the first place, to include digital ads, Deputy Premier Deb Matthews said Tuesday.

"It only makes sense when you've got legislation open that you address other problems in the act," she said.

The problems, as the government sees them, were that some ads were rejected for reasons they see as unnecessary. The new legislation will define partisan by banning the use of an elected member's picture, name, voice or the colour or logo associated with the political party.

Ontario is already a leader in banning taxpayer-funded partisan ads and these changes will strengthen the legislation, Matthews said. The federal Conservatives could take a lesson from Ontario's laws, she said.

"I have a huge problem with the federal government's advertising campaign, a huge problem with the amount of money they're spending on those campaigns," Matthews said.

The Harper government has booked $13.5 million for an all-out, co-ordinated blitz in April and May to advertise its 2015 pre-election budget. It comes amid increasingly vocal opposition to the government's use of taxpayer-funded advertising.

Federal economic action plan ads would not pass under Ontario's new legislation because the colour blue was used too much, she said.

Patrick Brown, the new leader of the Progressive Conservatives, and until he resigns his seat Wednesday still a member of the federal Conservative government as the MP for Barrie, said he doesn't think the federal ads were "overtly partisan."

Lysyk said in the 10 years since the advertising law has been in effect more than 7,200 ads have been approved and fewer than one per cent have been rejected. The only ad she rejected during her mandate was on a factual basis after she felt an ad suggested the hard-hit manufacturing sector in Ontario was booming.

She would not be able to reject that ad under the new legislation, she said.

If the Liberal changes to the advertising act are approved, Lysyk wants to be relieved of her duty to review government ads before they can run.

NDP Leader Andrea Horwath said the government is changing the law to make it easier for them to spend tax dollars on partisan advertising.

"That is wrong," she said. "It has no place in Ontario and shame on the government for doing it."