Legal professionals are among the most likely workers to do unpaid overtime, according to the Trades Union Congress (TUC).
A national study published this week found that 49.6% of legal professionals work unpaid overtime. Their average unpaid overtime, 9.7 hours a week, is exceeded only by financial institution managers and education professionals.
At a mean average pay of £27.60 per hour, this means that legal professionals lose an average of £13,921.44 a year, the TUC claimed.
It announced the figures to mark Work Your Proper Hours Day, on which it urged employers to thank staff for the extra work they are doing.
The TUC said that while much unpaid overtime is caused by heavy workloads, which employers need to manage better, much of it is also down to presenteeism - with staff judged on the hours spent at their desk rather than the work they do.
TUC general secretary Frances O'Grady said: 'A long-hours culture is bad for workers' health and their family life - whether the hours are paid or not.'