Washington ? The Justice Department on Tuesday notified an Arizona sheriff’s office known for its efforts against illegal immigrants that it has refused to cooperate with a civil rights investigation, is not in compliance with federal law and the department is threatening to sue.

Since March 2009, the U.S. Justice Department has been investigating Maricopa County Sheriff Joe Arpaio’s office in Phoenix for alleged discrimination and for unconstitutional searches and seizures. Arpaio says the inquiry is focused on his immigration efforts.

Robert Driscoll, a Washington lawyer representing Arpaio, said Justice Department lawyers “have picked the man and the department and are trying to find a violation, rather than find a violation and then seeking to vindicate someone’s rights.”

“They have been investigating for two years,” said Driscoll, who added that most people assume it has something to do with racial profiling.

But Driscoll said, “If it was going on now, presumably they would have evidence of this now.”

In a letter, assistant attorney general Thomas Perez, head of the Justice Department’s civil rights division, said the sheriff’s office is not turning over material that Perez’s lawyers are requesting. Over a year ago, Arpaio’s lawyers asked that the Justice Department’s Office of Professional Responsibility investigate alleged attorney misconduct regarding the investigation. In his letter to Arpaio’s lawyers, Perez said such “unfounded allegations” are not a basis for refusing to cooperate with the Justice Department probe.

In June, the office concluded that no civil rights division attorney at the Justice Department committed professional misconduct or exercised poor judgment in the probe of Arpaio’s office.

Perez gave the sheriff’s office until Aug. 17 to turn over documents first requested last year in what the department calls an inquiry into claims of discrimination based on national origin.

Arpaio and his legal counsel said a year ago that the sheriff’s office would not cooperate with the inquiry.

The office “has continued its unwarranted refusal to cooperate,” Perez wrote.

In June, the office supplied a position statement regarding the operation of its jail facilities.

The statement says “nothing at all about the allegations of discriminatory police practices,” and includes no agreement to provide access to sheriff’s office facilities and personnel, Perez said in the letter to the sheriff department’s legal counsel. The letter also said a limited production of accompanying documents fails to respond to the first request for material made 17 months ago.

Title VI of the Civil Rights Act of 1964 prohibits discrimination in federally assisted programs on the basis of race or national origin.