US Sheriff Joe Arpaio 'discriminated against Hispanics'
A lawman known for his tough stance on immigration has routinely discriminated against Hispanics, according to a federal investigation.
A US Department of Justice report found Arizona Sheriff Joe Arpaio's office had flouted US civil rights laws by racially profiling Hispanics.
Violations included unlawful arrest and detention, discriminatory jail practices and denial of services.
It comes as the Supreme Court reviews Arizona's tough immigration law.
Sheriff Arpaio has styled himself as America's toughest sheriff, and has been known to jail inmates in tents and dress them in pink underwear.
The justice department investigation into the Maricopa County Sheriff's Office (MCSO) was launched during the administration of President George W Bush.
Published on Thursday, its report requires the office to reform its practices or lose millions of dollars in federal funding.
The sheriff has until 4 January to say whether he will comply, or the federal government says it will sue him.
The justice department report says that in Maricopa County, Hispanics are four to nine times more likely to be pulled over by the police.
The sheriff's office also treats all Hispanics as though they are in the country illegally, says the report.
It highlights how language barriers have been exploited by the sheriff's deputies in the county jail.
Inmates with limited English were put in solitary confinement for up to 23 hours per day.
They were also locked in their jail cells for up to 72 hours for failing to understand commands in English.
The report cited a wide use by officers of racial slurs in emails and when speaking to inmates.
The justice department has said it is still investigating complaints of use of excessive force against Hispanics; sexual assault cases that were not properly investigated; and whether a "culture of bias" has deterred residents from reporting crimes.
The report links the malpractice to the sheriff himself.
"Arpaio's own actions have helped nurture MCSO's culture of bias," Thomas Perez, head of the justice department's civil rights division said.
"We found discriminatory policing that was deeply rooted in the culture of the department - a culture that breeds a systemic disregard for basic constitutional protections."
He added that the justice department's expert on racial profiling said this was the most serious case he had come across.
Republican presidential candidates have sought Sheriff Arpaio's endorsement to boost their campaigns.
This year, the lawman backed Texas Governor Rick Perry, who denounced Thursday's findings as politically motivated.
A federal grand jury has also, separately, been investigating abuse-of-power allegations at the sheriff's office and especially within his anti-public corruption squad.
Meanwhile, legislation from Arizona that aims to crack down on illegal immigration is pending before the Supreme Court.
The law would enable police to demand proof of citizenship from those they stop or detain, and to arrest suspected illegal immigrants without a warrant.