More on-the-clock time was spent by federal employees on union duties in 2010 but the rate of such “official time” per union-represented employee remained the same because the number of unionized employees also increased, the government has reported.

The Office of Personnel Management said that compared to fiscal year 2009, the number of union-represented employees in the non-postal federal workforce increased by about 26,000 to about 1,186,000, a 2.2 percent increase. Meanwhile, employees who serve as union officials spent nearly 3.1 million hours performing union duties on working time, a 2.4 percent increase over 2009.

The overall rate of official time remained constant at 2.58 hours per bargaining unit employee from 2009 to 2010, after dropping from 2.69 in 2007 and 2.60 in 2008.

Official time is time spent by federal employees performing representational work for a union in lieu of their regularly assigned work. It can be used for purposes such as conducting negotiations over a contract or representing employees in grievances and disciplinary matters, but not for internal union business such as elections or conventions.

Federal unions consider official time to be a tradeoff for the requirement that they represent all employees in a bargaining unit regardless of whether the employee pays union dues.

However, the practice has come under increased scrutiny this year, in part because of the cost in salary and benefits, which OPM said came to $137.4 million in 2010, up from $129.1 million in 2009. A House bill would end the use of official time for collective bargaining, and its sponsor earlier this year suggested ending official time entirely.

Bargaining accounts for about a tenth of official time use, dispute resolution about another 15 percent, and the rest is spent on general matters such as attending labor-management meetings, according to the OPM report.

The report also showed wide variation among agencies in the amount of official time used per bargaining unit employee. The National Labor Relations Board had the highest rate, nearly 11 hours, followed by the Railroad Retirement Board, the National Endowment for the Humanities, the Equal Employment Opportunity Commission and the Treasury Department at about 7 hours each, and the Housing and Urban Development and Transportation Departments and General Services Administration at about 6 hours each.

The rate at OPM itself also was above the average, nearly 5 hours.