LONDON — Increasing numbers of workplaces around the world are embracing technology, and a greater array of tasks is being automated. In the eyes of one major British labor organization, that need not be a threat to workers, but may instead offer an opportunity: less time working.

“I believe that in this century, we can win a four-day working week, with decent pay for everyone,” Frances O’Grady, the head of the Trades Union Congress, an umbrella group, said in a speech at the labor federation’s annual conference. That, she said, would help workers reap the benefits of technological change.

The economist John Maynard Keynes had predicted that people would eventually work for just 15 hours a week. Instead, technology has led to unpredictable, more intensive and longer hours at work, the Trades Union Congress said. “This is a return to the days of piecework, creating a culture where workers are required to be constantly available to work,” the group said in a report.

It is not the only organization scrutinizing how technology affects productivity and work-life balance.