SAN FRANCISCO — Orrick has joined a growing list of firms suing the city and county of San Francisco over objections to a voter-approved payroll tax on partner profits.

In a suit filed two weeks after Pillsbury Winthrop Shaw Pittman made a similar challenge, the firm is asking for a refund of the $610,127 it paid in payroll taxes in 2010 under Proposition Q, an ordinance voters passed in 2008 establishing a tax on profit distributions made to owners of so-called pass-through entities such as law firms. The new suit is Orrick, Herrington & Sutcliffe v. City and County of San Francisco,12-524003.