A judge refused Wednesday to halt an ethics investigation into alleged campaign finance disclosure violations by Democrat Caroline Fayard, her family and others during last fall’s lieutenant governor’s race.

The probe came to light during a state court hearing in Baton Rouge that began behind closed doors but was eventually opened to the public.

The hearing involved a lawsuit that the state Democratic Party, Fayard and others filed in late July against the Board of Ethics, the Supervisory Committee on Campaign Finance and others.

By law, the board acts as the committee.

Fayard is organizing a campaign to run for secretary of state this fall, the suit states.

“The filing of charges against Caroline for alleged violations of the (Campaign Finance Disclosure Act) will cause serious, immediate and irreparable harm to Caroline’s ability to be elected as Secretary of State …” the suit states.

State District Judge William Morvant initially sealed the suit at the request of the plaintiffs, shielding it from public view. The judge unsealed the suit Wednesday after listening to closed-door arguments from both sides.

Morvant agreed to seal Ethics Board subpoenas in order to protect the integrity of its investigation.

The rest of the hearing, during which attorneys for the plaintiffs argued unsuccessfully to put the brakes on the ethics probe, was open to the public.

Gray Sexton, a former longtime ethics administrator who represents Fayard and others in the suit, suggested after the hearing that Fayard may be the target of a “political vendetta.’’

“We’re concerned about where this investigation is allegedly proceeding,’’ he said.

Sexton and Mary Olive Pierson, who represents the Democratic Party in the suit, said no decision has been made about whether to appeal Morvant’s ruling.

Ethics Board Chairman Frank Simoneaux, who attended the hearing, called the judge’s decision a “complete victory’’ for the board and said the board is acting properly.

Simoneaux added that the board has made no decision on charges.

“There are no violations,’’ Pierson insisted, accusing the board of “grasping for straws.’’

“Every penny that was spent on this election has been faithfully and accurately and timely reported,’’ Sexton said.

The suit claims the Ethics Board has neither jurisdiction over alleged violations of the Campaign Finance Disclosure Act nor the power and authority to adjudicate any alleged violations of the act.

A 2008 state law removed the board’s authority to decide whether there have been violations of state conflict of interest, nepotism, campaign finance and other laws. That function was moved to a newly created Ethics Adjudicatory Board with the investigatory and prosecutorial functions.

Sexton argued in court Wednesday that the Adjudicatory Board is claiming that it lacks jurisdiction over matters involving the Campaign Finance Disclosure Act.

“There is no place for us to go for relief’’ once the Ethics Board probe is completed, he told Morvant.

Ethics Board attorney Harry “Skip’’ Phillips disagreed, saying the remedy would be the filing of a civil suit at the conclusion of the Ethics Board probe.

If after the conclusion of an Ethics Board investigation a hearing is requested, Morvant said, the matter would go first to the Ethics Adjudicatory Board.

Republican Jay Dardenne defeated Fayard, a political newcomer, in a runoff last fall in the lieutenant governor’s race.

Leading up to the election, Dardenne claimed Fayard’s family was trying to get around campaign contribution limits by funneling money through the state Democratic Party.

Dardenne complained that Fayard’s family was illegally earmarking the money it donated to the Democratic Party to be spent on Fayard’s campaign.

Dardenne said Fayard’s parents and businesses tied to them donated $210,000 to the Democratic Party’s PAC, then, a day later, the PAC bought ad time for Fayard costing $209,936. Fayard listed the ad time purchase as an in-kind contribution from the Democratic Party.

The suit’s plaintiffs include the state party’s political action arm and some of its contributors, including Fayard’s mother and father. Her father is lawyer Calvin Fayard.