A growing number of British workers are "close to breaking point," according to new research, which reveals that people are working harder, despite signs of a turnaround in the U.K.'s economy.
Some 40 percent of people said they were working harder than they were a year ago, recruiter Randstad said on Thursday, after carrying out a phone survey of 2,000 British employees.
And 43 percent of those questioned said they could not work any harder – a rise on 30 percent a year earlier - suggesting that more people are "working close to breaking point," according to the report.
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It comes despite signs that the U.K.'s economic recovery is picking up, with closely watched Purchasing Managers' Index (PMI) data beating expectations over recent months. Figures released on Thursday showed that activity in the services sector hit a 16-year high in the third quarter, boosting hopes of firm gross domestic product (GDP) growth this quarter, following a 0.7 percent expansion in the second three months of the year.
But businesses are still hesitant to hire new employees, according to Randstad U.K. CEO Mark Bull, meaning that "spread-thin" Britain was being stretched even thinner.
"Up until recently, firms were reluctant to take on staff because they were concerned the nascent economic recovery could be easily derailed," he said. "As a result, existing staff have taken on increasingly large workloads, particularly as the recovery has gained momentum and demand has increased."
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The survey's results serve to highlight the much discussed "productivity puzzle" in Britain – which has seen falling unemployment throughout the downturn, but anemic economic growth.
Economists attributed this phenomenon to falling productivity per worker, which was confirmed by data released by the U.K.'s Office for National Statistics last month.
The figures revealed that the productivity gap between Britain and other major economies in 2012 hit its widest level since 1994.
Output per worker in Britain was 19 percentage points below the average of the other G7 industrialized nations (Canada, France, Germany, Italy, Japan and the U.S.), and 2 percentage points lower than it was in 2007, before the financial crisis took hold.
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But Randstad's Bull insisted that low productivity did not mean that workers were not putting in the effort, adding: "The productivity problem is due to capital and human capital being stuck in less productive areas of the economy."
The U.K. had been too slow in shifting capital away from declining sectors and towards high-productivity ones, like the creative industries, high-tech manufacturing, IT and construction, Bull added.
"It has left too many workers stuck in sectors where productivity is low, when they should be in high-growth sectors where productivity per worker is much higher," he said.
—By CNBC's Katrina Bishop. Follow her on Twitter