Republican U.S. Senate candidate Tom Coburn (search), a physician accused of sterilizing a young woman without her permission 14 years ago, now says he has performed similar procedures on "lots" of underage women at their request.

In an interview this week on the Tulsa radio station KRMG, Coburn was asked: "To your knowledge, could this situation have happened, or has happened with any other women?"

Coburn replied: "I've done this lots to women who have come in with emergency things who have asked me to sterilize them, underage. When they've already had three babies."

Jay Parmley (search), state Democratic chairman, called Thursday on Coburn to detail "how many underage women he has sterilized."

Coburn spokesman John Hart said the candidate would not answer specific questions about how many medical procedures he has performed. "It's a deliberate effort on the behalf of Brad Carson to avoid talking about his liberal voting record," Hart said.

Coburn and Carson, a Democrat, are locked in a tight Senate race for the post Republican Don Nickles is leaving after 24 years. The race could be pivotal in the battle for control of the Senate.

The campaign became even more divisive with the emergence of details about the sterilization 14 years ago.

Coburn performed the procedure on the woman during an operation to remove an ectopic pregnancy, a dangerous condition in which an embryo was growing in her fallopian tube. He surgically removed the tube and tied off her other fallopian tube, leaving her sterile.

The woman says she never consented to the procedure. He said he got oral permission for the sterilization, but a nurse failed to get written consent.

Coburn has said he intentionally did not report the sterilization on a Medicaid reimbursement to ensure the woman would not have to pay for the procedure. Coburn said his political foes are pushing the issue to hurt his campaign even though the women's 1991 lawsuit over the matter was dropped.

Parmley said Coburn's remarks about the other sterilizations raise "serious questions" about "values and ethics," especially if Medicaid funding was involved.