By Mary Wisniewski

(Reuters) - The Michigan legislature will consider a proposal this week that, if enacted, would make it the ninth state to prohibit insurance companies from offering abortion services unless women pay an extra fee in addition to the usual premium.

The proposal will go before the majority-Republican legislature as a petition organized by Right to Life of Michigan, an anti-abortion group, that was approved on Monday by the Michigan Board of Canvassers.

Under Michigan's constitution, the legislature could approve the proposed "Abortion Insurance Opt-Out Act" by a simple majority vote that does not require the signature of Republican Governor Rick Snyder.

Snyder, who identifies himself as pro-life, vetoed a similar measure lawmakers approved less than a year ago. He said in a letter to constituents that the bill went too far because it treated situations involving rape and incest as elective abortions, and because it interfered with the private insurance market.

"Michigan citizens do not want to pay for someone else's abortion with their tax dollars or health insurance premiums," Right to Life of Michigan President Barbara Listing said in a statement. "Abortion is not health care; abortion kills a living, developing human being."

The Michigan petition is one of a series of state initiatives in recent years that attempt to limit abortions, including banning the procedure after 20 weeks and enacting new restrictions on abortion providers.

Eight states now have similar abortion insurance laws, according to Elizabeth Nash, state issues manager for the Guttmacher Institute, a pro-abortion rights research group.

Nash said the Michigan proposal would force women to decide to purchase the additional coverage without knowing whether they would ever need an abortion, and would not allow a woman to buy coverage after getting pregnant by any means, even rape.

"Seeking an abortion isn't something that anyone plans for," Nash said.

Story continues

Michigan House Democrats slammed the petition in a statement, saying it would hurt victims of rape and incest.

"Right to Life wants to further traumatize these women by denying health care coverage to terminate a pregnancy forced upon them in the most heinous of circumstances," said Rep. Pam Faris, a Democrat.

The Michigan legislature will receive the petition on Tuesday after returning from a two-week break. If the legislature rejects it, or does nothing with the proposal in 40 days, it will be put to a statewide vote on the November 2014 ballot.

The petitioners submitted about 316,000 signatures - only 258,088 were required for it to be approved for consideration, according to the state elections board. The signatures submitted represent about 3 percent of Michigan's population of 9.9 million.

(Reporting by Mary Wisniewski; Editing by David Gregorio)