OTTAWA - Lisa Raitt finally said sorry Wednesday for her controversial comments, but the tearful regrets did little to silence critics who accused her of presiding over an escalating crisis affecting thousands of cancer patients.

The embattled natural resources minister and other Conservative cabinet members struck back and blamed the medical isotopes crisis on the former Liberal government, which is over three years out of office.

Raitt offered a belated and emotional apology for describing the shortage of isotopes used in cancer tests as a "sexy" issue from which she could benefit politically.

"Today, I want to personally convey my deep regret for wording I used in a private discussion earlier this year which was inadvertently recorded," she told a hastily arranged news conference.

She had refused to apologize a day earlier despite heavy criticism from the opposition and the public. Outraged cancer survivors and their supporters demanded Raitt resign -- or at least apologize -- for remarks they considered to be insensitive and calculating.

It's not clear what changed overnight, other than growing public outrage.

Raitt choked up as she described watching her father die of colon cancer when she was a child, and then losing her brother to lung cancer as an adult.

"As somebody who has been, in their personal life, deeply affected by cancer, my intent was certainly not to show any disrespect for cancer victims, survivors or their families," she said.

"I want to offer a clear apology to anyone has been offended by what I said."

She left without taking any questions and has yet to explain why she didn't apologize sooner. She later made calls to three organizations, including the Canadian Cancer Society, to personally apologize.

In the House of Commons, Raitt launched an attack on the Liberals, accusing the former government of knowing in 2003 that a project to replace the aging Chalk River, Ont. nuclear reactor -- which produces one-third of the world's isotopes -- was doomed to failure.

She said the Liberals were either "ignorant to the situation, or not caring themselves."

That prompted an explosion from Liberal Ralph Goodale, who was natural resources minister at the time.

"All of the crises have happened on their watch, not on our watch," he shouted. "It's time to get serious."

It was left to Prime Minister Stephen Harper to cool the partisan rhetoric during an availability with Columbia's president. Harper said he wasn't pointing the finger at the Liberals because for "whatever reason" the reactor replacement project hasn't worked despite hundreds of million of taxpayer dollars in research.

Harper said there are no easy or short-term fixes, adding it's likely Canada will eventually get out of the isotope-production business once Chalk River is permanently closed and new sources of supply come on line.

Hospitals across the country are being forced to delay or cancel diagnostic tests that rely on isotopes, leaving thousands of cancer and heart patients scrambling for alternatives.

Health Minister Leona Aglukkaq tried to reassure the public, saying alternative procedures that don't rely on nuclear medicine are being recommended to the health community.

But Liberal MP Keith Martin, a medical doctor, said other methods are nowhere near as effective or accurate.

Raitt made her controversial comments in January in a private conversation with her aide which was accidentally caught on tape. The tape was misplaced by the aide, Jasmine MacDonnell, and fell into the hands of a reporter for the Halifax Chronicle-Herald.

MacDonnell resigned last week after it was revealed that sensitive documents about the future of Atomic Energy of Canada Ltd. were mistakenly left behind at a TV news bureau for a week following an interview.

In the tape, Raitt says the isotope issue is hard to control, "because it's confusing to a lot of people."

She then adds: "But it's sexy ... Radioactive leaks. Cancer."

She also expresses doubts about the parliamentary skills of Health Minister Leona Aglukkaq.

Raitt has also come under fire for $80,000 in travel and hospitality expenses rung up in two years in her former job as CEO of the Toronto Port Authority.