State employees whose domestic partners and children receive health insurance coverage are going to have to get married if they want to keep those benefits after January 2014.

The administration of Gov. Martin O'Malley made the decision after same-sex marriage became legal in Maryland in January. O'Malley had previously extended the health benefits to domestic partnerships in 2009, and he was a strong proponent of legalizing same-sex marriage through the 2012 legislative process and the failed attempt to defeat the new law on last year's ballot.

"When the state opened enrollment to same sex domestic partners and their children in 2009, the rationale was that these individuals could not legally marry in Maryland, and therefore did not have access to the same benefits that heterosexual couples could attain through marriage," O'Malley spokeswoman Raquel Guillory wrote in an email. "Once same sex couples could marry in Maryland in January of this year, that rationale no longer applied."

However, the move has drawn the ire of some of O'Malley's supporters who stood with him through the legalization of same-sex marriage and November's referendum fight.

"There are a lot of assumptions that everything now is a level playing field. We're getting there, but we're not there yet, so we just want employers to be cognizant of that," said Carrie Evans, executive director of Equality Maryland.

"We want people to be able to make their decision to marry their partner based on the reasons different-sex couples make that decision, not to keep health care for their partners."

Evans said that because the federal government and 40 other states don't recognize same-sex marriages, a couple who married in order to keep health benefits would find it more difficult to divorce in a state that doesn't recognize their marriage.

Guillory said the state could be open to lawsuits by heterosexual couples whose partners are not entitled to health benefits unless they are married if it doesn't make the change.

"If the state fails to take action to repeal same sex domestic partner benefits, we would have a system under which same sex couples are eligible for health benefits through marriage or a domestic partnership, but opposite sex couples are eligible only through marriage -- thereby creating an inequity that would likely be subject to legal challenge," Guillory wrote,

The change would affect fewer than 300 current state employees or retirees. Maryland will stop accepting applications for domestic partnerships next month, but couples in a domestic partnership will receive health benefits through December.