WASHINGTON -- Employers in industrialized countries are increasingly using computers, cameras and listening devices to snoop on employees and monitor their performance in the workplace, the International Labor Organization said.


A report released this week said that 19 countries were experiencing an increase in surveillance, including Japan and the Netherlands, where 88 percent of all electronic monitoring systems have been installed since 1980, and 57 percent since 1985.


But the survey of 393 firms in Canada, Europe and the United States said that two-thirds of them considered electronic monitoring to be ineffective or even counterproductive.


The organization, based in Geneva, is an agency of the United Nations. It includes representatives of governments, labor and business.


Technological advances have made it possible for employers to gain insight into almost every aspect of a worker's activities on the job, the report said.


"It doesn't matter whether you work in a factory, in an office or as a highly paid engineer or professional," said Michelle Jankanish, a co-author of the report. "You are very likely under observation" in any of these places, "by computers or machines controlled by your boss."


American workers are probably facing the greatest loss of privacy among the industrialized nations covered by the report, it said. It cited a U.S. survey suggesting that as many as 80 percent of employees in telecommunications, insurance and banking are subject to telephone or computer-based surveillance.


The survey of 301 U.S. companies estimate that 20 million Americans -- one-sixth of the workforce -- may be subject to some form of electronic monitoring.


The report expressed particular concern about employer access to electronic mail, which it said was recording dramatic growth.


The organization contended that "the chemistry of intrusion" is yielding few practical benefits for employers, and may contribute to a fall in productivity.


"Companies like to engage in such monitoring, even though many admit the practice elicits little or no useful information," Jankanish said in an interview.


Spying on employees was a major contributor to increasing stress in the workplace, the report said. Monitored workers reported "boredom, high tension, extreme anxiety, and depression, anger and severe fatigue" which adversely affected their performance on the job, according to the report.