The Trades Union Congress (TUC) has urged employers to allow staff to continue to access social networking sites at work.
"Simply cracking down on the use of new web tools like Facebook is not a sensible solution to a problem which is only going to get bigger," said TUC general secretary Brendan Barber.
"It is unreasonable for employers to try to stop staff from having a life outside work, just because they cannot get their heads around the technology.
"Better to invest a little time in working out sensible conduct guidelines so that there do not need to be any nasty surprises for staff or employers."
The TUC's announcement follows news that 50 per cent of companies block staff access to social networking sites because of the possible impact on productivity and security.
Andrew Brown, technical manager at internet security firm SonicWall, suggested that both sides have a point but that controlling access to online content is not the problem managers seem to think it is.
"Content management systems allow threats to be excluded and web content to be accessed only when desired, for example limiting access to social networking sites to lunch breaks," he said.
"It also provides content filtering to ensure that no undesirable content is downloaded to company websites at any time."
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