Employers are not getting the most of out employees who work long hours, it has been warned today.
Online jobs firm TipTopJob.com conducted a survey of more than 1,000 UK workers found that more than one in 10 Welsh people worked over 80 hours a week.
"Unless you choose to or you work in a sector that has its own special contractual hours, you should not have to work more than 48 hours a week," said Corinne Dauncey, of TipTopJob.com.
"While working long hours is becoming more and more common as industries become more competitive, it is important to ensure that you have a work/life balance to enable you to relax, enjoy leisurely activities and spend time with your family and friends outside of the office.
"Working long hours will ultimately affect your health and cause you to become stressed, which will neither be productive in your working or personal environment."
Welsh people have the longest working week in the UK, often putting in twice as many hours as staff in other parts of Britain.
Employees from Wales have a working week of between 50 and 80 hours, compared to an average of between 30 and 50 in the Midlands, London, the North West and South West, the study found.