The federal government says it has no choice but to reluctantly keep distributing to millions of waterfowl hunters a toll-free phone-sex-service number that features a breathy woman promising callers that they can "talk only to the girls who turn you on" for $1.99 per minute.

About 3.5 million federal "duck stamps," featuring artwork by a Plymouth artist, are affixed to a card that bears the misprinted number, the U.S. Fish and Wildlife Service said Wednesday.

All waterfowl hunters age 16 and older must buy and carry the current Migratory Bird Conservation and Hunting Stamp, commonly known as the duck stamp. Sales of the stamp raise about $25 million each year to fund wetland habitat acquisition for the national Wildlife Refuge System.

Rachel Levin, a Fish and Wildlife spokeswoman, called the misprint, which connects callers to a phone-sex service, "an unfortunate typographical error" that her agency "really regrets." She adds that the agency will keep selling the $15 stamps with the naughty number because reprinting the card would cost too much.

The correct number, 1-800-STAMP24 (1-800-782-6724), is for people wishing to order additional duck stamps. Levin said two digits of the phone number are transposed on the card that holds the self-adhesive version of the stamp. That incorrect number, 1-800-872-6724, translates to 1-800-TRAMP24. Callers to "Intimate Connections" are warned that they must be 18 years or older before proceeding.

Levin doubted that the digits were purposely transposed. "As far as we know," she said, "it was just an error."

The stamps were produced by Ashton Potter Ltd. of Williamsville, N.Y. Messages left with Ashton Potter's executives were not returned.