The U.S. health insurance industry denounced a White House decision to let people losing their insurance buy bare-bones plans or even go without insurance. The industry said the surprise Thursday night announcement -- four days before the Monday deadline for people to choose coverage that begins Jan. 1 -- upends assumptions insurance carriers made when setting premiums for 2014. "This latest rule change could cause significant instability in the marketplace and lead to further confusion and disruption for consumers," said Karen Ignagni, president of America's Health Insurance Plans, the industry's national political advocacy and trade association. The new rule will let any consumer whose current, substandard insurance plan is being canceled claim a "hardship exemption" and buy a bare-bones "catastrophic plan" if standard health plans sold through the new federal and state marketplaces are more expensive than their previous plan. "This is a commonsense clarification of the law," Health and Human Services spokeswoman Joanne Peters said. "For the limited number of consumers whose plans have been canceled and are seeking coverage, this is one more option," she said. HHS Secretary Kathleen Sebelius said the goal was to ensure "the smoothest possible transition" for people seeking new coverage after cancellation of their policies. Sebelius' department issued a bulletin late Thursday advising consumers, "If you have been notified that your individual market policy will not be renewed, you will be eligible for a hardship exemption and will be able to enroll in catastrophic coverage." Catastrophic plans were previously limited, under the Patient Protection and Affordable Care Act, or "Obamacare," to people under age 30 or those who qualified for a set of specific hardship exemptions. But now, under the broadened definition of hardship, people who buy catastrophic plans will be exempt from the penalty imposed on many Americans who don't have coverage starting in 2014. HHS said it was setting up a hotline, at 1-866-837-0677, for people who got cancellations and wanted to take advantage of the new option. Sebelius disclosed the policy shift in a letter to Democratic Sens. Mark Warner and Tim Kaine of Virginia, Angus King of Maine, Mary Landrieu of Louisiana, Jeanne Shaheen of New Hampshire and Heidi Heitkamp of North Dakota. The senators -- all facing tough re-election campaigns next year or in states Obama lost in last year's election -- urged Sebelius in a letter Wednesday to allow the rule changes, citing "our constituents who are upset by the cancellation of the health plans." The senators said in a joint statement late Thursday they were "pleased that the administration appears to have responded to the concerns we've raised." It wasn't immediately clear how many people might qualify under such an arrangement. The administration said Thursday it believed fewer than 500,000 people whose existing coverage had been terminated hadn't yet enrolled in another plan.