Sheriff Joe Arpaio has sent letters to current and former attorneys in the Maricopa County Attorney's Office warning them to watch their words if they speak to investigators looking into possible unethical conduct by former County Attorney Andrew Thomas.

The letter threatens the attorneys with criminal charges if they reveal "confidential" information about the sheriff's inquiries into county Supervisors Don Stapley and Mary Rose Wilcox and Superior Court Judge Gary Donahoe.

Interim County Attorney Rick Romley responded with a letter of his own warning Arpaio that he was overstepping the authority of his office.

In late March, Arizona Chief Justice Rebecca White Berch appointed a Colorado attorney to conduct the investigation. John Gleason, who handles such inquests for the Colorado Supreme Court, has been in Phoenix in recent weeks to work on the case. Gleason could not comment because of his own ethical obligations.

On May 3, Arpaio mailed letters to current and former county attorney staffers, saying, "This letter is intended to advise you that I do not consent to you revealing any information provided to you by my office, regardless of any personal incentive to breach the attorney-client privilege."

At the end of the letter, he wrote, "Be advised that should you disclose any information that could harm any pending criminal investigations, I will consider charging you with violations of applicable statutes."

Phil MacDonnell, Thomas' former chief deputy, received one of the letters. "It gave me pause," MacDonnell said.

However, Romley fired off a letter to Arpaio citing case law and informing him that the relationship between the two offices is not attorney and client but law enforcement and prosecutor. Citing case law, Romley said that the County Attorney's Office "does not render legal services to the investigators."

As for the threat to file criminal charges against anyone who testifies to the Bar, Romley wrote, "This threat is not only inappropriate but is a clear abuse of your authority as sheriff of Maricopa County. Thereby, I shall be forwarding your letter" to the U.S. District Attorney's Office.

Republic reporter JJ Hensley contributed to this article.