Professor Simon Folkard of Swansea University, who was asked to present a medical case to the court, compared it to the effect of alcohol on driving. "We can't put our hands on our hearts and say that's the perfect limit but we can say there's a need for limits," he said yesterday.
"One of the things my group is trying to do is establish a link between disturbed sleep at one end and increased cardiovascular risk at the other. There is some evidence that disturbed sleep results in chronic fatigue, which results in psychological problems, which results in gastro-intestinal problems, which may result in cardiovascular problems."
He added that a finer examination of the effects of long working hours showed an "exponential function", in that working one hour over 40 may have very little impact on a worker, whereas one hour added onto a 60 hour week could have a "massive effect".
"The evidence suggests that if people work excessive hours they have health and safety problems. Forty-eight hours seems a very reasonable limit to me," Prof Folkard said.
Professor Malcolm Harrington of Birmingham University was asked by the then Department of Employment to review the existing evidence on whether the Working Time Directive could be based on health and safety issues.
Although he concluded that it was "difficult" to fix an exact number of hours, as there was no specific scientific evidence to back it, he said that a 48 hour limit was not unreasonable - and that the figure should be "certainly not much higher".
"If you look at more than 56 hours, there is a lot of evidence that [that] would be detrimental. If policy makers then say 48 hours it doesn't bother me.
"I think it comes down to the fact that if you want to interpret science and give it to a policy maker you would have difficulty disputing the justification for fixing numbers," he said.
While he could see no justification for advocating a specific length of holiday, working breaks, or length between shifts, Professor Harrington, who claims his position on the issue has been widely misrepresented, believes setting a 48 hour week is about "the bottom line - protecting those who can't protect themselves".
"I happen to believe, now looking at the evidence, that the hours of the working directive can be justified as a health and safety measure."
He is currently researching the effects of long working hours on white collar workers and their companies.
Meanwhile, Chris Cardell, a business stress management consultant, believes that despite being widely criticised by business leaders, the implementation of a 48 hour week, would be a "blessing in disguise" for British firms.
He said absences from work through stress and stress-related illnesses cost UK businesses pounds 7 billion a year, and the new law could save money.Reuse content