The federal Conservative party has sent a threatening email to the widow of an asbestos victim in the latest chapter of Canada's debate over the hazardous mineral.

A top Tory official is warning the woman to stop using the party logo in an online ad campaign against the controversial industry -- a campaign she started after her husband died of an asbestos-related cancer.

Michaela Keyserlingk, whose husband Robert died in 2009 of mesothelioma, has been running an online banner since the spring that reads, "Canada is the only western country that still exports deadly asbestos!"

Conservative party executive director Dan Hilton warned Keyserlingk to stop using the Tory symbol immediately.

"Failure to do so may result in further action," Hilton wrote in a July 29 email which carried the subject title, "Unauthorized use of trademark." The email, which The Canadian Press obtained from Keyserlingk, went on to advise her: "Please govern yourself accordingly."

The exchange comes as Canada faces intensifying international criticism over its asbestos exports and the Quebec government mulls whether to help revive one of the country's last-remaining mines -- a decision that could come as early as Monday.

Canada, which barely uses the hazardous material domestically, exports the bulk of its asbestos to poor countries.

Industry proponents insist the material is safe if properly handled -- but its critics stress that the product is used mainly in developing countries where safety standards are haphazard.

A growing chorus of health experts, and people like Keyserlingk, want to see the industry shuttered for good.

The Conservatives, meanwhile, have steadfastly defended asbestos exports and insist they're safe when handled properly.

Keyserlingk's blurb, which she says appears randomly on Canadian web pages, is flanked with a "DANGER" warning label and an image of the Tories' official symbol: a blue letter C with a Maple Leaf. It also directs readers to her website.

"I just want to have the asbestos trade stopped because it's such a horrible death," said Keyserlingk, who doesn't belong to any organization and pays more than $300 per month for the ad out of her pocket.

"It's just so terrible -- and to even contemplate doing that to other people is unforgivable."

When asked about the ad, the Conservative party stood its ground.

"The Conservative logo is a trademark of the Conservative Party of Canada and we do not allow its unauthorized use," party spokesman Fred DeLorey wrote in an email to The Canadian Press.

Hilton did not respond to requests for an interview.

As for Keyserlingk, she isn't ready to back down.

She said she'll only cancel the ad if a high-ranking member of the Conservative party meets with her to explain why it supports the industry. She would be happy to take the issue up with Prime Minister Stephen Harper himself -- in person.

"I have no permission to use (the logo) and they have a legitimate argument against me... But on a human level they have no legitimacy whatsoever," the Ottawa resident said.

Keyserlingk didn't show much concern when asked about the prospect of legal action against her.

"That would not be very bright of them to sue me," she said. "What will they get out of me? It's not as if there are millions sitting here."

Keyserlingk said she has tried unsuccessfully for years to contact the Tories over this issue.

Before he died in December 2009, her husband also wrote letters to Conservative ministers and to Harper himself, demanding that he put an end to asbestos exports.

His widow said he received a response from the Prime Minister's Office, which said Harper did not have time to answer his letter.

Coincidentally, Keyserlingk said her husband was the Progressive Conservative riding president in the 1970s for Ottawa-Centre -- the riding around Parliament Hill.

She said he used to pound the pavement with Tory candidates. And he continued to support the party.

"He stayed a true-blue Conservative," she said, before adding what she thought his reaction would be to the party's steadfast backing of the asbestos industry.

"He would be utterly disgusted -- it's not what he thought the Conservative party would be about."

Keyserlingk said her husband, who died at age 76, inhaled asbestos fibres while working summer jobs on Canadian naval ships when he was a student.

The marathon runner led a healthy life until one day he had trouble breathing and was diagnosed with a form of mesothelioma, a cancer caused mainly by asbestos exposure. He battled the disease for two-and-a-half years, she added.

"And then he died a horrible, horrible death -- I mean these people suffocate," she recalled. "It's awful to watch. I hope he didn't feel as much as we saw when we had to watch him.

"None of us can forget how he died."

The banner ad includes a web address for her website, where she's posted information on asbestos, links to news stories and an essay about her husband's battle against asbestos-related cancer.

Keyserlingk's son designed the ad at her request. She chose to include the Tory symbol to catch the eye of conservative Canadians in hope of luring them to her website, so they could learn about the party's stance on the issue.

The ad has also proven to be effective: she says traffic to her website doubles when the ad is online.

Canada's asbestos industry has nearly disappeared in recent decades amid health concerns. The Canadian Cancer Society estimates that more than 100,000 people die worldwide every year from occupational exposure to asbestos.

The vast majority of Canadian asbestos exports come from an operation in Thetford Mines, Que., but investors are hoping to save the Jeffrey Mine in nearby Asbestos, which has operated infrequently in recent years.

Quebec has promised to back a contentious $58-million bank loan to prolong the life of Jeffrey Mine for another 25 years, as long as the company can find enough private financing.

The company has requested an extension for the Monday deadline set by the government.

Whatever happens, Robert Keyserlingk's wife of 47 years will keep fighting.

"I owe him not to give up because he never gave up," she said.