The Internal Revenue Service on Wednesday adopted a strict definition of affordable health insurance, one which family advocacy groups say will deny federal financial assistance to millions of Americans with modest incomes who cannot afford family coverage offered by employers, The New York Times reported.

The policy decision came in a final regulation interpreting ambiguous language in the 2010 health-care law.

In deciding whether an employer's health plan is affordable, the IRS said it would look at the cost of coverage only for an individual employee, not for a family. Family coverage might be prohibitively expensive, but federal subsidies would not be available to help buy insurance for children in the family.

"This is bad news for kids," said Jocelyn A. Guyer, an executive director of the Center for Children and Families at Georgetown University. "We can see kids falling through the cracks. They will lack access to affordable employer-based family coverage and still be locked out of tax credits to help them buy coverage for their kids in the marketplaces, or exchanges, being established in every state."