The number of federal employees and job applicants filing complaints of job discrimination increased in 2010 by 3.75 percent over the previous year, according to a new report from the Equal Employment Opportunity Commission.

The most common allegation was retaliation against employees who complain about discrimination, according to the report issued Wednesday.

“The federal government should be a model workplace,” said Dexter Brooks, director of the EEOC’s Federal Sector Programs. “We are concerned that retaliation is the most common basis of discrimination alleged, and we caution all federal agencies to make sure that reprisals do not become the usual response to complaints of discrimination.”

Federal agencies continue to struggle with a backlog of discrimination cases. The average time for conducting investigations dropped from 185 days in 2009 to 181 days in 2010, but the average total time it took for closing cases increased from 344 to 360 days.

Only 3.3 percent of the 7,053 cases closed on the merits in 2010 resulted in findings of unlawful discrimination.

After retaliation, age and race were the most frequent grounds for discrimination cases. Each was up 5.1 percent in 2010 from the previous year, according to the report.