WASHINGTON (AP) -- Federal job discrimination complaints rose to an all-time high last year, led by an increase in bias charges based on religion and national origin.

The Equal Employment Opportunity Commission received nearly 100,000 charges of discrimination during the 2011 fiscal year, the most in its 46-year history. That's a slight increase over the previous year, which had 25 fewer complaints.

Charges of religious discrimination jumped by 9.5 percent, the largest increase of any category. Claims of bias based on ancestry or country of origin rose 5 percent.

Experts say the increase reflects the growing diversity of the nation's work force.

"We're seeing a greater diversity among minority groups in America," said Ron Cooper, a former general counsel of the EEOC who now works in private practice. "We're seeing more workers from India, Pakistan and other countries that bring additional religious complexity to the work force."

The commission does not specify which religious or ethnic groups filed the most charges.

As in past years, claims based on race, sex and retaliation were the charges filed most often, according to commission data.

Charges of racial bias fell by 1 percent, while sexual discrimination claims fell 2 percent and sexual harassment claims dropped 3 percent.

At the same time, claims of disability bias climbed 2 percent and charges of discrimination based on age rose 1 percent.

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