Maryland health exchange workers are focusing the next few days on calling and emailing thousands of uninsured people to see if they need coverage for this month and to let them know they have until Tuesday at 5 p.m. to sign up for private health insurance that would be retroactive to Jan. 1.

To qualify, Marylanders must prove that they tried unsuccessfully to get health insurance through the state’s marketplace before the new year began, and they must be willing to pay premiums for January and February before Feb. 15. For those that get in, the insurance will cover medical expenses incurred this year.

Maryland Gov. Martin O’Malley (D) and Lt. Gov. Anthony G. Brown (D) announced the last-minute change on Tuesday, just as Brown headed into testify before legislators about emergency legislation that would set up a different form of retroactive health insurance.

That option, which lawmakers are on track to approve as early as this week, would expand enrollment in a state insurance program — the Maryland Health Insurance Plan — which opened in 2003 to cover residents who couldn’t get insurance elsewhere, often because of a pre-existing condition. The program’s premiums are usually higher than private plans, and officials have said that they expected people to stay on the plan for only a few months at most, before transitioning into a private plan.

Brown originally said that anywhere from a few hundred to 5,000 people could sign up for that insurance option, which could have cost the state as much as $10 million. But now that people can obtain retroactive insurance through the private companies, Brown said that he only expects “a few hundred” will enroll in the state’s insurance program.

All four insurance companies that are participating in Maryland’s exchange — CareFirst, Evergreen Co-op, Kaiser Permanente and United — have agreed to provide the retroactive insurance.

Still, there could be people who do not sign up for that insurance before the Jan. 21 deadline or who could fall through the cracks in some other way, so Brown said there is still a need for the emergency legislation to set up a final “safety net” or a “backstop” to protect them.

”This is an opportunity for the state to step up and fullfil its responsibility,” Brown said. “It’s short-term. It’s temporary.”

But the legislation, which is simply written to ensure quick passage, prompted some concerned questions from lawmakers. Several asked what safeguards would be in place to protect against people signing up fraudulently, while a few worried it might be too difficult for legitimate applicants to get coverage.

State officials have yet to say exactly how applicants would prove that they tried to get insurance through the exchange and were stymied, although affidavits have been mentioned. Once the legislation is passed, state health officials say they will create such standards and policies.

The Maryland Attorney General’s health unit sent a letter Tuesday to leaders of the committees vetting this legislation that voiced “serious concerns that the bill lacks important implementation provisions and safeguards for the most vulnerable consumers.”

Assistant Attorney General Patricia F. O’Connor wrote that the bill should be updated to explain how people would prove that they tried using the exchange, provide a time-frame for how long this program would last and address other logistical problems.

Del. Susan W. Krebs (R-Carroll) mentioned the letter during a Md. House of Delegates Health and Government Operations Committee hearing.

“The devil has been in the details on implementation,” she said, “so I am worried about implementation of this new little program.”

Other lawmakers raised questions about the financing of this short-term fix, which once was estimated to cost $5 million to $10 million. That money will come out of the Maryland Health Insurance Plan’s fund, which has tens of millions of dollars available that were largely collected through a tax on hospitals. Plus, Brown said, those enrolled will have to pay premiums.

“This option is not free insurance,” Brown said.

The Senate Finance Committee also held a hearing on the emergency legislation on Tuesday, and then voted 9-to-1 to advance an amended bill to the Senate floor. The legislation could pass as early as this week.

Brown reiterated Tuesday that the number of people who might enroll in this program will likely be “dramatically” lower than initially estimated thanks to the private insurance carriers agreeing to offer retroactive coverage through the exchange.

Del. Heather Mizeur (D-Montgomery) has called for those insurance providers to extend the deadline to sign-up for retroactive coverage. At a press conference on Wednesday, she pointed out that the new offer has yet to be promoted on the exchange’s homepage and “unusually long” waits at call centers have deterred some residents.

“A retroactive grace period is the right approach,” Mizeur said. ”But who thinks that providing it for one week is actually going to net us very many new covered families?”