PORTLAND — The Maine Turnpike Authority alleged Tuesday that its former executive director misused nearly $500,000 in turnpike funds in the form of gift cards, credit card charges and vacation and sick leave pay to which he wasn’t entitled.

In a lawsuit in Cumberland County Superior Court, the agency raised new allegations of misspending and fraud against Paul Violette — including that he was overpaid by $161,000 for unused vacation time and sick leave after falsely claiming he hadn’t taken any vacation or sick days during his 23 years at the agency.

The lawsuit asked the court to freeze $450,000 worth of Violette’s assets to satisfy the claims. As a lawyer and former legislator who once served as Senate majority leader, Violette should have known better, the suit says.

“With his distinguished educational and public service background, he should have known better than to misuse his position as executive director to convert Maine Turnpike Authority funds to his own personal use, benefit and enjoyment,” the suit said.

The state attorney general’s office is conducting a separate criminal investigation into the matter.

Violette’s attorney, Peter DeTroy, said he had been told that a civil suit would probably be filed.

“Some of it we’ve seen it before. Some of it’s new,” DeTroy said. “But I’m not going to comment on it because of the potential outstanding criminal investigation.”

Violette resigned in March from the authority, which oversees the 106-mile Maine Turnpike, following questions about gift cards for upscale hotels and restaurants he bought with turnpike funds. He said he gave the cards to civic and charitable groups so they could give them away for fundraisers, but he couldn’t document where they went.

An investigation by the state Office of Program Evaluation and Government Accountability showed that the authority purchased at least 1,461 gift cards valued at $162,300 between 2000 and 2010. But OPEGA was able to verify that only a small number of them were received by charitable and civic groups from which the office requested records.

Tuesday’s lawsuit brings forth new allegations regarding Violette’s use of turnpike authority credit cards and payments he received for unused vacation and sick days.

From 2003 to 2010, Violette charged $24,819 on authority credit cards and redeemed more than $90,000 worth of gift cards for personal travel, hotel and meal expenses on trips in Maine, Florida, Bermuda, Canada, France, Puerto Rico, Spain and Italy, the suit alleges. The complaint further claims he spent another $143,479 in “abusive credit card expenses” without evidence they were spent for legitimate businesses purposes.

The lawsuit also accuses Violette of abusing a turnpike authority policy, in place since 2006, to pay employees for unused vacation time and unused sick leave.

Violette received $184,889 for unused vacation time and $130,729 for unused sick leave after he said he hadn’t taken any vacation time or sick days since he joined the agency in 1987, according to the complaint. But Violette, in fact, had used vacation and sick days and as a result of his false statements was overpaid $161,000, the suit says.

The suit conceded Violette may be able to provide evidence that some of the unaccounted gift cards or $143,000 in “extravagant” credit card expenses were “innocent and justifiable.” Even so, the authority is seeking $450,000, a figure that includes $35,000 in audit expenses to review Violette’s spending.

Peter Mills, who was appointed interim executive director after Violette resigned, said the turnpike authority board directed him to explore the possibility of recovering turnpike funds if an audit determined they had been misappropriated.

“The board back in March gave me this task to pursue and it’s just now coming to fruition,” he said.