BOSTON (AP) – Gov. Mitt Romney asked Massachusetts’ highest court Friday to force a proposed anti-gay marriage constitutional amendment onto the state’s 2008 ballot if the Legislature fails to vote on it.

The Republican Romney and 10 other petitioners filed their complaint with the Supreme Judicial Court – the same court that ruled 4-3 in 2003 that the state could no longer deny marriage licenses to gay couples.

The governor, a vocal opponent of gay marriage and a possible presidential candidate in 2008, was incensed after the Legislature recessed a constitutional convention on Nov. 9 without taking a vote on the amendment. The move was widely seen as a way to kill the measure.

About 170,000 people signed a petition to have the amendment placed on the ballot. Romney accused lawmakers of shirking their constitutional duty and claimed the constitution does not give them the option of avoiding a vote on a qualified initiative petition.

“The Legislature took an oath to uphold the constitution,” said Eric Fehrnstrom, a spokesman for Romney, who was visiting two of his sons in southern California on Friday.

“This is no longer just about gay marriage,” Fehrnstrom said. “It’s about the right of the people to participate in their own government.”

Massachusetts Gay and Lesbian Political Caucus co-chair Arline Isaacson said the complaint has no merit and accused Romney, who steps down as governor on Jan. 4, of using the gay marriage issue to enhance his political standing among right-wing voters nationwide.

“Romney is pursuing this aggressively because he seeks to keep his name front and center at the national level as an anti-gay zealot in order to court conservative voters around the country,” Isaacson said. “This is a badge of honor for him.”

Among those joining Romney as plaintiffs in the petition are former SJC Justice Joseph Nolan and former Boston Mayor Raymond Flynn.

The complaint filed on Friday asks the SJC to order Senate President Robert Travaglini to hold a vote of the combined House and Senate when the constitutional convention reconvenes on Jan. 2, the final day of the legislative session. The initiative needs approval of only 50 of the 200 legislators during the current session, then again in 2007, to continue to the November 2008 ballot.

If the Legislature still does not vote Jan. 2, the petition asks the SJC to instruct Secretary of State William Galvin to place the question on the 2008 statewide ballot.

Galvin spokesman Brian McNiff said Galvin’s office would not comment while the case was pending.

Travaglini, D-Boston, could not be reached for comment.

Attorney John Hanify, who represents Romney and the other anti-gay marriage petitioners, said the case will be heard initially by an SJC single justice. No hearing had been scheduled as of Friday.

Hanify said the complaint presents the court with a sticky legal issue involving separation of powers among equal branches of government because the petitioners are asking the judiciary to instruct the Legislature how to proceed.

But he said the Legislature’s inaction requires the court to step in.

The Legislature used the tactic of recessing without voting on a similar question in 2002, and also to block ballot referendums on a number of other controversial topics such as abortion and term limits for office holders.

The Nov. 9 recess mirrored action taken during a July constitutional convention at which the gay marriage amendment was up for consideration.

“Rather than do their duty and take the vote they’re require to take, they punt,” Hanify said.

Isaacson accused Romney of singling out the gay marriage issue for political gain while ignoring other citizen initiative petitions – such as one that would make health care a constitutional right, which the Legislature also did not vote on.

The amendment would define marriage as being exclusively between one man and one woman, but would allow gay people who already are married to remain married.

Opponents of the amendment, including powerful House Speaker Salvatore DiMasi, D-Boston, feared they didn’t have the 151 votes needed to kill the measure and instead called for a vote to recess the joint House-Senate session.

Lawmakers approved the recess vote, 109-87.