Workers on average also say they spend 42 minutes a day on personal tasks, for total "wasted time" of more than eight hours per work week on activities unrelated to the job.

"It's understandable that employees may occasionally use their mobile devices or attend to personal tasks during business hours — but these activities can easily become big distractions," says Brandi Britton, a district president for OfficeTeam. "To best manage their time, staff can take advantage of breaks during lunch and throughout the day to catch up on non-work email or errands."

Not surprisingly, the age group that racks up the most time are employees ages 18 to 34, spending on average 70 minutes on mobile devices and 48 minutes on personal tasks each work day.

For all employees, workers are most occupied by personal email on their mobile devices (30 percent), while 62 percent of managers think staff spend the most time on social networks when using their own mobile devices during business hours.

Other survey findings include the following:

• Male employees most frequently check non-work email on their cell phones (32 percent), while females browse social networks more (33 percent).

• Workers reported social media (39 percent) and entertainment websites (30 percent) are most commonly blocked at their companies. Nearly half of respondents (48 percent) indicated their organization doesn't restrict access to online content.

• More than half of professionals (58 percent) often use their personal devices at work to visit pages that are banned by their company, a 36-point jump from a 2012 survey. Only 39 percent of managers think it happens that commonly.

• Sixty-eight percent of male workers frequently use their cell phones to access blocked websites in the office, compared to 43 percent of females.