TORONTO - Ontario is looking into whether American money is being used to pay for television advertisements attacking the McGuinty government, says Finance Minister Dwight Duncan.

The Canadian Transit Company is paying for the ads that accuse Ontario's Liberal government of wasting billions of dollars on an unnecessary "road to nowhere" which the province says will lead to a new bridge between Windsor and Detroit.

The company describes itself as the Canadian half of the Detroit-based firm that owns the Ambassador Bridge joining the two cities.

Ontario's election finances law allows third parties to buy and air campaign advertising, but not foreign companies.

"I'm sure probably legally, they've set it up in a way that protects them, but that's something I ought to look at and probably will because they are clearly trying to influence an election," said Duncan.

The owners of the Ambassador Bridge don't want the competition from a new bridge and are fighting hard on both sides of the border to try to protect their monopoly, added Duncan.

"Bring it on," he said. "This is American money. They moved all their employees to the American side. I've been fighting them for seven years. They've been trying to stop us at every step of the way."

However, the Ambassador Bridge Company said the ad has nothing to do with Ontario's upcoming election, and is more about generating a public debate on a $2.2-billion access road to the proposed bridge.

"This ad isn't necessarily against the bridge, it's more against the spending of over $2 billion on a road in Windsor to a bridge that doesn't exist," said vice-chair Matt Moroun. "One of the primary reasons for getting the ad out is to make sure people were aware of it so they can ask questions, review it and form their own opinions."

Moroun dismissed Duncan's suggestions the ad is about protecting the monopoly of the Ambassador Bridge, noting there is also a tunnel between Windsor and Detroit and the Bluewater bridge crossing at Sarnia.

The Progressive Conservatives tried this year to put limits on third-party advertising, mainly to reign in the Working Family Coalition, which has spent millions in recent Ontario elections on advertising that supports the Liberals and attacks the Tories. The Tories' efforts were thwarted by the Liberals, who are now on the uncomfortable end of a third-party attack, said PC critic Lisa MacLeod.

"They had an opportunity to vote for legislation that would have curbed this type of interference, but they voted it down," she said. "The reality here is for once (Premier) Dalton McGuinty and Dwight Duncan see that money might attack them."

Construction on a Windsor approach road for the new bridge will break ground in weeks, and the project will mean thousands of jobs for Ontario and a huge shot in the arm for the local economy, said Duncan.

Moroun was surprised to hear construction on the road would start before Michigan has given final approval to the new bridge.

"I think that should cause a lot of people to ask a few questions," he said. "Like we've been told a number of times, it's not possible to build half a bridge."

The New Democrats also support the construction of the new international bridge, but believe the Liberals should have done more to secure support for the project south of the border. The NDP said the Liberals celebrated the completion of the agreement rather than doing the lobbying work in Michigan needed to seal the deal.

The television ads also go after Duncan personally for supporting the new bridge, but the finance minister said he's not worried about getting re-elected in his Windsor-Tecumseh riding on Oct. 6.

"I don't think Canadians will be intimidated by these kinds of scare tactics," he said. "In my community the biggest question I get is: how soon, how soon, how soon?"

The Canadian Transit Company donated more than $28,000 to the Liberals between 2003 and 2007, while giving only $2,000 to the Progressive Conservatives. The Tories say even former supporters of the Liberals now believe it's time for a change, and are taking advantage of third-party spending rules to attack the ruling party.

"It's very hypocritical at this time for them to be crying foul, and they should understand that they have reaped what they have sown," said MacLeod.