There are more employees who work unpaid overtime (49%) than receive overtime pay (23%), according to the study.
Workers who regularly work unpaid overtime do an average of three hours extra a week for free (184 minutes).
Only a third (36%) take their full lunch break every day.
The employees most likely to work the longest extra hours unpaid include senior managers (averaging 4.1 hours a week), remote workers (3.5 hours), and those working in legal services and education (4.1 hours and 3.9 hours respectively).
Claire Williams, chief people officer at Ciphr, said employers must ensure they do not create a culture which makes people feel compelled to work extra hours.
She said: “Doing a bit of extra work occasionally is one thing – and it is relatively common practice to work additional hours, at times, to fulfil your role – but feeling like you ‘have’ to do that extra work regularly because it is being expected of you is quite another.
“The issues occur when unpaid overtime is both very frequent and excessive and when employees aren’t taking enough breaks and the downtime they need.
“That’s when the employer needs to recognise that there’s an underlying problem – usually, but not always, workload-related – that needs to be urgently addressed.”
More on overtime:
UK employees worked £26 billion in unpaid overtime in 2022
Men working more overtime than women
Almost half of parents work overtime to cope with workload
Nicholas Le Riche, partner at law firm BDB Pitmans, said employers need to be careful that employees obey working time regulations which mandate at least a 20 minute break every six hours.
There is also a limit on working more than 48 hours a week and the right to 11 consecutive hours of rest a day.
Employees can opt out of the 48 hours a week limit but there is no opt for the other two obligations.
Speaking to HR magazine, Le Riche said: “It can be difficult for employers to ensure that their employees are not working in breach of the daily and weekly limits, especially now that hybrid and other flexible working arrangements are so common.
“However, active management by stressing the importance of staff taking regular breaks, emphasising that emails received outside of normal hours don’t have to be immediately responded to and looking for signs that staff are working excessive hours can all help.”
He added that employment law may evolve in the future to create better work-life boundaries in the age of remote work.
He said: “The problem of excessive hours is increasingly a political issue with both Labour and the Scottish government considering the introduction of a legal right to disconnect outside of working hours similar to those already introduced in France and other European countries.”
