The U.S. Justice Department plans to file a civil lawsuit against Maricopa County, Arizona, and Sheriff Joe Arpaio over civil rights violations.

In a letter sent Wednesday to an attorney for the Maricopa County Sheriff’s Office, Assistant U.S. Attorney General Thomas Perez writes that the county’s failure to address racial discrimination and other violations found by the federal government in December will go to litigation.

The sheriff’s policies are unconstitutional and in violation of federal law, and compliance “cannot be secured through voluntary means,” the letter said.

As a result, the Justice Department will file suit against the county, the sheriff’s office and Arpaio.

The December letter from the Justice Department described “a pervasive culture of discriminatory bias against Latinos at MCSO that reaches the highest levels of the agency.”

The 22-page document said detention officers in Arpaio’s jail invoked offensive slurs and profanities against Hispanics.

“Sheriff Arpaio’s own actions have helped nurture MCSO’s culture of bias,” the letter said.

For example, the sheriff apparently endorsed one constituent’s letter asking for a “round-up” at one Phoenix street corner of “dark-skin(ned)” people: Arpaio told a member of his command staff in a note to “(h)ave someone handle this,” the Justice Department said.

Arpaio has denied any discrimination, and one of his attorneys called the Justice Department investigation a “witch hunt.”

In December, Arpaio pledged to continue working with the Justice Department on the issues, but this week’s letter announcing the lawsuit states that didn’t happen.

Despite requests, Maricopa County officials and Arpaio have not met with the Justice Department since February 6, the letter said.

The Justice Department drafted an agreement to address its findings and wanted to negotiate it with the sheriff’s office, but the sheriff’s office called off the negotiations, the letter said.