Firms that let employees access Facebook and other social networks are suffering when it comes to staff productivity, says Nucleus Research.

According to the IT research company, by allowing access to Facebook, firms are losing an average of 1.5 percent in total employee productivity. The study also revealed that 77 percent of workers with access to social networks visit them during work hours.

Nucleus Research also said "some" employees use Facebook for up to two hours a day at work, although the company did not say how many workers fit into that category. Of those using Facebook at work, 87 percent said they had no clear business reason for using the site.

"If your company is facing tight margins and low profitability, as many are now, then how can you accept any work distractions that drain your overall productivity?" said Rebecca Wettemann, vice president of research for Nucleus Research.

"While it won't make you popular, restricting Facebook can reclaim lost productivity. If your profitability is say two percent, this could be the difference between staying open or closing shop."

Facebook, which logged its 250 millionth user earlier this month, has been showing tremendous growth.

Last week, Nielsen Online reported that people spend more time on Facebook than any on other website. Nielsen also reported that Facebook saw a 700 percent increase from April 2008 to April 2009 in the amount of time users were spending on the site.

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