Everett Mayor Carlo DeMaria says he will not return $180,000 in bonus pay that a state investigation found to be an overpayment until he gets “due process” and a chance to challenge the findings, according to a letter his lawyer sent the city council.

The response challenged the legitimacy of the conclusions of the Office of the Massachusetts Inspector General, an independent agency that looks for fraud and waste in public funds. In the letter, posted on the city’s Facebook page Wednesday evening, attorney Young Paik said the mayor hadn’t been allowed “to provide meaningful input, to confront witnesses … or to contest the conclusions” before the report was issued.

The response came one night after the council voted to demand he return the funds to the city treasury within 30 days, one of a series of recommendations based on the Inspector General Jeffrey Shapiro’s report.

In February, Shapiro submitted his investigation finding that DeMaria had worked with city council to establish “longevity payments” to reward his years of service, and then received more money than he was due and concealed the overpayments from the council. DeMaria was first elected in 2007.

The mayor disputed these findings and said he has been completely transparent about the payments.

DeMaria did approve the city spending $150,000 for an audit recommended by the inspector general to look into all payments made to the mayor since 2016 to search for other overpayments. He also said he would work with the council on its request to separate the duties of the city auditor from the chief financial officer’s office.

City councilor Katy Rogers said she was pleased with DeMaria’s support of better auditing, but said his response to the repayment demand suggests “this will involve a long and drawn-out legal process, which is understandably frustrating for our community.”