WASHINGTON — New evidence has been filed in a long-running civil rights case against the Secret Service, including e-mails that portray an offensive image of a naked black man and racist jokes.

Among the 10 e-mails submitted to the court were jokes circulated within the agency that made fun of the way a "20-year-old 5th grader" in Harlem spoke; the Rev. Jesse Jackson; and a black golf caddy's work ethic.

"We are deeply disappointed by any communication or action on the part of our employees that exhibits racial or other insensitivity. We expect our employees to show better judgment," agency spokesman Eric Zahren said. "The Secret Service has a zero-tolerance nondiscrimination policy. We do not and will not tolerate bias and discrimination of any kind."

In 2000, a group of black employees filed a lawsuit that alleges that since at least 1999, black agents have been passed over for promotions because of their race. The plaintiffs also claim their white colleagues and supervisors regularly use a racial epithet to refer to criminal suspects and black leaders of other countries. The lawsuit claims the Secret Service has always had a discriminatory culture.

Zahren said the 10 e-mails filed in court came from a comprehensive search of more than 20 million electronic documents over a 16-year period. "These e-mails are in no way a reflection of the agency or its policies or culture," he said.

Attorney E. Desmond Hogan said the Secret Service has been covering up evidence for years. He accused the Secret Service of dragging its feet by refusing to turn over documents and has asked a federal judge to resolve the dispute so the case can go to trial.

Last month, an employee found a noose in one of the Secret Service's training centers. The employee who tied the noose out of canine training rope has since been placed on administrative leave, according to the agency.

In 2007, 80 percent of the people who worked at the Secret Service were white, and 10 percent were black, according to data obtained by The Associated Press. Ten percent were of other races. In the agency's senior leadership, whites made up about 75 percent and blacks 13 percent. Black people make up about 12 percent of the United States' population.

The Secret Service investigates counterfeiting cases and protect presidents, vice presidents, their family members and other dignitaries. The agency became part of the Homeland Security Department in 2002. It was previously part of the Treasury Department.

The lawsuit was filed in the U.S. Court of the District of Columbia.