BOSTON (AP) – Supporters of a measure to ban same-sex marriage sued in federal court on Dec. 13, seeking as much as $5 million in damages from lawmakers who blocked a final vote last month on the proposed constitutional amendment.

The lawsuit, filed in U.S. District Court by Voteonmarriage.org, argues the 109 lawmakers violated the supporters’ rights to free speech, to petition the government and to due process under the law.

The group is asking the court to interpret the vote to recess a joint meeting of the House and Senate as a vote in favor of the amendment, even though many lawmakers said the vote was designed to kill the amendment. Opponents feared they didn’t have the 151 votes needed to kill the measure and called for the vote to recess.

The legislature is scheduled to take up the question again Jan. 2, the last day of the session. Supporters fear lawmakers will again avoid taking a vote, killing the proposal.

Glen Lavy, a lawyer representing Voteonmarriage.org, says the lawsuit is needed to force lawmakers to follow the constitution. It seeks $500,000 from the lawmakers for the cost of the group’s legal battles and another $5 million in punitive damages. The damages would be split 109 ways, and lawmakers would be held personally liable, he said.

“We would like to put an end to the Massachusetts legislature thumbing its nose at citizen initiatives,” Lavy said. “This lawsuit is about holding those legislators responsible for their illegal conduct.”

Lavy said he didn’t expect a ruling before Jan. 2. He called the request that the court interpret votes to recess as votes in favor of the amendment “a unique request for relief” and acknowledged it was a long shot.

Kyle Sullivan, spokesperson for House Speaker Salvatore DiMasi, declined to comment, citing the pending litigation.

Another lawmaker named in the suit, Newton Democrat Ruth B. Balser, said she was unfazed by the threat of punitive damages.

“I am very confident that every action that we have taken here in the Massachusetts legislature is consistent with the Massachusetts Constitution,” she said.

It is the second lawsuit designed to force lawmakers to take a vote on the question.

Gov. Mitt Romney and other opponents of same-sex marriage filed a suit with the state Supreme Judicial Court asking the court to force lawmakers to vote on the proposed amendment or, if they fail to act, to put the question on the 2008 ballot anyway. The case is pending.

Massachusetts in 2003 became the only state to allow same-sex marriage. Vermont and Connecticut permit civil unions, California grants similar status through a domestic-partner registration law, and more than a dozen states give same-sex couples some legal rights.