The American Civil Liberties Union has called on the U.S. Senate to pass legislation that would prohibit local, state and federal law enforcement agencies from racially profiling suspected criminals.

Sen. Ben Cardin (D-MD) introduced the End Racial Profiling Act in 2011, but the bill has not yet been taken up by the Senate Committee on the Judiciary.

"For more than a century black men and women traveling through predominantly white neighborhoods have been questioned for no reason – simply because police officers felt they didn‘t belong there," the ACLU said in a letter (PDF) sent to senators. "During the past decade, as international terrorism has become a subject of intense concern, those of Arab and South Asian descent have been spied upon, stopped, questioned and subjected to intensified police scrutiny based on racial characteristics rather than any evidence of wrongdoing."

"Most recently, local police in Alabama have been circulating in predominantly Hispanic neighborhoods, telling folks to go inside their homes or possibly face arrest – because the state passed a law requiring police to verify the immigration status of people who they stop or arrest."

The End Racial Profiling Act would prohibit law enforcement agents from stopping investigating, arresting, or detaining an individual based on his or her race, ethnicity, religion, or national origin.

It would also mandate training on racial profiling issues as part of federal law enforcement training, and require local and state departments to adopt measures to eliminate racial profiling as a condition of receiving federal funding.

The ACLU said racial profiling was unconstitutional violated international standards against non-discrimination and undermined the nation's human rights obligations.

"Without a comprehensive federal law that includes a strong enforcement and oversight mechanism, racial profiling will continue to plague our communities and our citizens," the group said. "Federal legislation is key to ending racial profiling in this country."