PROVIDENCE, R.I. — Prosecutors have asked a federal appeals court to dismiss an attempt by a former civilian employee of the U.S. Navy to get a shorter sentence for orchestrating a long-running $18 million kickback scheme.

In a filing with the 1st U.S. Circuit Court of Appeals on Thursday, government lawyers say Ralph M. Mariano waived his right to appeal the 10-year prison sentence when he signed a plea deal and should not be granted an exception. If he is allowed to appeal, they say, he is not entitled to a more lenient sentence because he failed to accept responsibility after his guilty plea, claiming, among other things, that the crimes never happened.

Mariano has asked the appeals court to send his case back to the district court for resentencing. He says prosecutors and U.S. District Judge Mary Lisi unfairly did not give him credit – and a lesser sentence – for accepting responsibility because of complaints he made about alleged prosecutorial misconduct. He sent the complaints to the Justice Department and Lisi.

As part of his agreement to plead guilty to conspiracy, theft of government property and tax evasion, Mariano agreed to continue to accept responsibility through his sentencing. In return, the government agreed to recommend a more lenient sentence. But prosecutors declined to do that at sentencing, telling the judge that Mariano had explicitly denied the scheme in the misconduct complaints.

Lisi said she had not read the complaints, but agreed with prosecutors that “he’s done just the opposite” of accepting responsibility. She sentenced him to 10 years, a month shy of the maximum.

Mariano asked that he be resentenced and that the judge take into account his misconduct complaints or disregard his complaints and award him credit at sentencing for accepting responsibility. That would reduce his maximum prison term to seven years and three months.

Mariano worked for the Navy in Washington and lived in Virginia. The scheme also involved people and companies in Georgia and Rhode Island.