SAN DIEGO >> The first U.S. Navy admiral convicted of a federal crime while on active duty was sentenced today to 18 months in prison for lying to investigators about a Malaysian defense contractor at the center of a massive corruption scandal.

Robert Gilbeau was sentenced today in San Diego after pleading guilty to one count of making false statements.

“This is the first time our nation will incarcerate a Navy admiral for a federal crime committed during the course of his official duty, and it is truly a somber day,” Acting U.S. Attorney Alana W. Robinson said in a statement. “When tempted by parties and prostitutes, one of our most respected leaders chose karaoke over character, and cover-up over confession, and in doing so he forever tarnished the reputation of a revered institution.”

Gilbeau wrote in a letter to the judge that he was “devastated” by the situation in which he finds himself.

“I have no one to blame but myself,” he wrote.

He added that the media has “painted me to be corrupt and despicable” but he is “still proud” of his service.

Gilbeau was convicted in June after admitting that he lied when he told federal agents that he had never received any gifts from Leonard Glenn Francis. The Navy allowed him to retire in October but reduced his rank from rear admiral to captain.

Nicknamed “Fat Leonard” because of his wide girth, Francis has admitted to bribing Navy officials with more than $500,000 in cash, prostitutes, and other gifts in exchange for classified information to help his company, Glenn Defense Marine Asia. He is awaiting sentencing.

Francis and his company that supplies food and fuel to ships overbilled the Navy by more than $34 million, prosecutors said.

According to the government’s sentencing memo, Gilbeau spent years accepting cash, and having Francis foot the bill for late-night partying at nightclubs and karaoke bars, fine dining, luxury hotels and prostitutes.

In exchange, Gilbeau signed off on Francis’ company invoices that grossly overbilled the Navy.

In one instance, Gilbeau signed an invoice for the USS Nimitz that was the highest amount the Navy ever paid per day for wastewater removal in the history of the ship. Prosecutors said evidence suggests the company kicked back $40,000 in cash to Gilbeau. Gilbeau denied the allegation.

When investigators started investigating the scandal, Gilbeau repeatedly lied to investigators about his relationship with Francis, though the two had known each other since 1997. He also destroyed documents and deleted computer files to conceal the relationship after Francis was arrested during a visit to San Diego in 2013, according to court records.

U.S. District Judge Janis L. Sammartino said Gilbeau carried out “a systematic destruction of records.”

“You violated the law,” she said. “You dishonored your shipmates, the Navy and the United States of America.”

Gilbeau is the highest ranking military member sentenced in one of the Navy’s worst corruption cases.

Twenty current and former Navy officials have been charged so far. Ten have pleaded guilty.

Five Glenn Defense Marine Asia executives and the corporation have also pleaded guilty.

AP writer Elliot Spagat contributed to this report.