Supporters of a proposed constitutional amendment to ban gay marriage on Thursday asked a justice of the state's highest court to force lawmakers to take action on the ballot question, and if they fail to do so, to order it put on the 2008 ballot anyway.

Gov. Mitt Romney and other gay marriage opponents filed a motion 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 — after lawmakers postponed action on the question until January.

Backers of the question, which would define marriage in Massachusetts as the union of a man and a woman, gathered more than 170,000 signatures of people in support of the proposed amendment, which would ban future gay marriages in Massachusetts but leave existing same-sex marriages intact.

John Hanify, an attorney for Romney and others who support the measure, told Justice Judith Cowin the Legislature has a history of ignoring voter-initiated petitions. Lawmakers declined to vote on a similar question in 2002, and used similar tactics to block ballot referendums on a number of other controversial topics such as abortion and term limits for office holders.

"They've done it repeatedly. They've done it incessantly," he said. "It will persist if the court doesn't intervene."

Under the constitution, the anti-gay marriage question needed the backing of just 50 of 200 lawmakers in the current two-year legislative session. It then would come up for a second vote in the new legislative session where it would also need the backing of 50 lawmakers.

Opponents of the question, 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 from Nov. 9 until Jan. 2.

Lawmakers approved the recess vote by a majority of 109-87. The move was widely seen by both supporters and opponents of gay marriage as a way to kill the measure.

Supporters of the proposed amendment say marriage is a fundamental building block of society, and voters — not a single judge majority — should decided whether to change the definition.

Backers of gay marriage say minority civil rights should never be put to a popular vote.

Hanify asked Cowin to order Senate President Robert Travaglini to call for a vote. Failing that, Romney's petition asks the court to order Secretary of State William Galvin to put the question on the 2008 ballot anyway.

Assistant Attorney General Peter Sacks said separation of powers and the court's own precedent indicate the court should not force the lawmakers to vote.

"The request for relief to try to force the joint session to take action is squarely barred," he said.

Sacks referred to a case brought in 1992 by supporters of a term limits question. Lawmakers killed the question by refusing to vote on it.

In that case, Sacks said the court decided against trying to force a vote citing the separation of powers and noting that while the constitution gives the governor a role in the process, there is no direct role for the judiciary.

Hanify said the 1992 case differs because lawmakers adjourned the session, giving the governor the right to call them back. In the gay marriage case, lawmakers have simply recessed.

Hanify conceded that asking the court to bypass the Legislature and put the question on the 2008 ballot would be "a more extraordinary remedy."

Kris Mineau of the Massachusetts Family Institute, which supports the measure, said such a move is needed to counter "the horror story of the last 20 years of this Legislature refusing to honor the citizen's right to petition."

The case could end up being consolidated with a lawsuit filed by the Committee for Health Care for Massachusetts, which is pushing a constitutional amendment guaranteeing access to affordable health care.

The group is also asking the justices to require Galvin to put the question on the 2008 ballot, after lawmakers avoided taking a final vote on the proposed amendment.

Cowin, one of the four justices who ruled gay marriage is legal, said she was considering taking the question to the full court. She made no immediate ruling.

Since gay marriage became legal, more than 8,000 same-sex couples have tied the knot in Massachusetts, the only state to allow gay marriage.

Romney, whose term ends Jan. 4 and has been laying the groundwork for a possible 2008 president run, was in Miami on Thursday attending the Republican Governors Association meeting.