Gov. Paul LePage's administration is facing a potential loss of federal funding to administer its food stamp program over concerns about state's decision to put photos on cards used to access the benefits.

Federal officials said in a letter to the Maine Department of Health and Human Services on Thursday that recipients are being given information that makes it seem like they're required to have their photos placed electronic benefit transfer cards, even though the program is voluntary.

The Republican governor's administration must make it clear to recipients that their decision to not have their photo placed on the card won't affect their benefits, said Kurt Messner, Northeast regional administrator for the U.S. Department of Agriculture's Food and Nutrition Service.

Mary Mayhew, commissioner of Maine's Department of Health and Human Services, accused the federal government of trying to prevent "accountability and reform in the nation's welfare system."

The USDA is demanding that LePage's administration outline within 45 days how it plans to correct the several issues cited in the letter and says failure to do so could cause Maine to lose federal funding for the program.

The loss of funding could be significant. In fiscal year 2013, the federal government paid about $8.9 million, about half the cost of administering the program in the state.

The Portland Press Herald first reported about the letter Friday.

Despite urgings from federal officials to delay, LePage's administration began putting recipients' photos on the cards in July, saying it would help the state prosecute those who illegally sell the cards for drugs or cash.

A spokesman for the Maine Health Department said 21,000 people have chosen to put their photos on the cards, while 100 have declined.

Federal officials said the state's policy raises significant civil rights concerns and could have a "chilling effect" on parents applying for benefits for their eligible children if the parent fears they have to have a photo placed on the card.

They said the state must also make clear to retailers that people other than the person whose photo is on the card are allowed to use it as recipients often allow their kids or neighbors to buy food for them if they're sick or otherwise can't make it to the store.

Chris Hastedt, policy director for Maine Equal Justice Partners, said even those who agree with the state's decision to put photos on the cards should be concerned that the way it's being implemented is putting up barriers for people who need help paying for food.

Maine officials dismissed the criticism and said the department will respond to the federal government to "set the record straight."

"We do not believe that a policy putting photos on EBT cards has a `chilling effect' on their appropriate use any more than putting photos on drivers' licenses has a `chilling effect' on driving," Mayhew said.