The global study of 29 countries, 40% of UK employees think that they are underperforming if they do not respond to phone calls and emails straight away, whether in the office or at home.
One in five said that workloads mean they have to respond to messages even during meetings and half reported that they felt they had to deal with work-related matters outside of office hours.
On a global scale, the UK ranks closely alongside its peers. The proportion of employees in Germany, France and the USA that believe they are constantly on call is within five percentage points of that in the UK.
But UK workers appear to feel the most pressure to respond. 94% of British workers who receive messages from work out of office hours also deal with other work-related matters in their private time. This is much higher than the 83% of US workers, or 86%of French workers, who do the same.
Mark Bull, CEO of Randstad UK and Middle East, said: "UK employees are being hit hard by increasing workloads as teams operate more leanly in the economic downturn and digital technology makes them constantly available.
"Fielding phone and email messages in business meetings was previously considered the height of rudeness; now it is common practice. Our research indicates the increased pressure to process emails immediately, wherever employees are.
"Organisations face a challenge to ensure that their workforces remain motivated and do not suffer from information overload. There is a real danger that spread thin Britain could well turn into burn out Britain."