As farmers and trade unions warn that the Trans-Pacific Partnership could cost jobs in the auto and agriculture sectors, sources say the secret proposal would be a boon to Canadian exporters.

CTV News has learned all tariffs would be removed on a majority of Canadian industrial products, including metals and minerals, petroleum products, potash, steel, chemicals, plastics and industrial machinery, according to a source close to the negotiations.

Canada currently exports about $158 billion annually of those goods to the other 11 countries involved in the talks, and that figure would likely increase after the elimination of tariffs.

Trade Minister Ed Fast is attending discussions in Atlanta, Ga., where an agreement in principle could be reached as early as Friday by a dozen Pacific countries, including the U.S., Japan and Australia.

At a campaign stop in Vaughan, Ont., Conservative Leader Stephen Harper addressed concerns that the agreement might hurt Canada's auto industry.

"This government is fully committed to making sure we have a strong and viable auto industry," he said. "Our auto industry exports 85 per cent of its products. That's why we make sure that in all of these negotiations we secure markets for our auto industry, (and) that we're part of the global trading system.

"We will only sign a deal if it's in the best interest of all of the Canadian economy including our auto industry," he said.

Harper also said the Conservatives are the only party that can deal with tough trade negotiations.

"Unlike the other parties, we're not going to walk away from a trade negotiation at the first sign of worry,” he said.

Unifor, Canada's largest private-sector union is campaigning against the Conservatives, and wants the other parties to back away from any deal that it believes would negatively impact the auto industry.

Its president, Jerry Dias, said the Conservatives should release the full text of the TPP deal before election day.

"This government thinks they're going to close the deal, they're going to have a photo-op to say, 'Look, we just signed a deal,' without any intention of sharing the details with Canadians," Dias told The Canadian Press.

"They're not going to get away with it. They're going to have to tell the dairy farmers what's in the deal. They're going to have to tell the auto-parts companies what's in the deal."

Dias' main concern is Japan's lobbying efforts for the easing of "rules-of-origin" requirements, which would allow the country to export vehicles to North America with fewer Canadian-made parts. He's concerned this provision will lead to trouble for Canada's auto industry.

Adam Taylor, former adviser to Fast, countered that argument on CTV’s Power Play, where he said that Canadian auto companies would benefit from selling more in places like Japan.

“You forget that you’ll gain access to all those other countries,” said Taylor, who now works for consulting firm Ensight Canada.

“(Japan is) the third largest economy in the world,” he added. “Gaining a preferential foothold into that market will been a boon for the auto sector.”

Canada's dairy industry has also been discussed during the TPP negotiations.

In particular, other countries have asked for more access to Canada's dairy sector, which could impact ridings in Quebec and Ontario where dairy is a major industry.

On Tuesday, dairy farmers staged a protest against the agreement on Parliament Hill. Farmers have expressed concerns that the government will make concessions on supply management, which protects the Canadian dairy market from foreign producers.

At a campaign event in Winnipeg, Liberal Leader Justin Trudeau said that there should be more transparency when it comes to trade negotiations. He said the Conservatives have not been open enough, causing uncertainty among those affected, including dairy farmers.

“Yes, we need to protect our existing systems, which work to ensure that our agricultural communities and farms continue to be able to feed the rest of us in the country,” Trudeau said. “But at the same time, we need to do that in an open and transparent way.”

"Yet again, we have a prime minister who is engaged in the kind of secrecy and non-transparency that leave a lot of people uncertain, when we need a prime minister who is making the case for trade, and pointing out how many jobs come through trade," Trudeau added.

Taylor also downplayed the potential impact on farmers, saying the Comprehensive Economic and Trade Agreement between Canada and the European Union has proven that free trade deals can be signed while “maintaining the (supply management) system.”

During Monday evening's Munk Debate, the proposed TPP deal also came up, with NDP Leader Thomas Mulcair noting that he doesn't trust the Conservatives to protect the dairy industry.

“I asked Mr. Harper last night to clearly state whether he supported supply management in its entirety and he skated,” Mulcair said Tuesday from a campaign stop in Iqaluit, Nunavut.

“We’re going to be asking questions that are important to people in the auto sector, questions that are extremely important to people who live under supply management,” he added.

Green Leader Elizabeth May also told CTV’s Power Play Tuesday that there are “a lot of reasons to oppose the TPP.”

May argued that, in addition to hurting the dairy and egg industries, the TPP would increase pharmaceutical prices, empower foreign corporations to sue in Canada and impact crown corporations.

With files from The Canadian Press