Long working hours are once more in the news, as the European Commission tries to limit the time employees spend at work.
The Commission says it wants to close loopholes in the EU's Working Time directive, changes which would mean workers would only be able to work more than 48 hours a week if employers and unions reach a collective agreement.
The CBI, which represents employers, says the matter should still remain one of "individual choice" and the TUC says the changes "satisfy no-one".
Under current legislation, UK workers can volunteer to put in more than the standard EU maximum of 48 hours a week.
The TUC reckons that nearly four million UK employees - about 15% of the total workforce - are regularly working more than 48 hours a week, and the total has fallen by only 7% since the directive was introduced in 1998. Well-paid professionals
As unions and business debate the merits of the changes to the law, closer analysis reveals that a broad spectrum of UK workers work long hours.
According to labour market think tank, The Work Foundation, these workers fall into two very different groups - with high earners at one end of the scale, and lower earners at the others.
"You have people in the city, lawyers and other professionals, who are very highly paid," said Work Foundation spokesman Adam Worth.
"They get very high rewards for working very high working hours, and are quite prepared to be flexible. They will have high levels of autonomy and work satisfaction. Their working ethics may also mean they have to provide flexibility."
He added: "If you are a lawyer and your income is based on bookable hours, then you are going to work longer hours."
With the UK moving from a manufacturing to a service economy, he foresaw people in the service sector, such as public relations and marketing, working longer hours.
"The IT sector is another instance where you might find people earning rather well, but they will be there from 7am until late at night."
Those in the printing industry can also earn big if they work long hours. Hospitality industry
At the other end of the scale, there are low earners, who may need to put in extra hours so they can have a reasonable standard of living.
"People in the hospitality sector, such as hotel workers, put in very long hours, as do construction workers - who may be on site during the week and then the weekend," said Mr Worth.
He said factory workers may also work more than 48 hours a week - some work in larger organisations with union representation and agreements in place, while others lacked formal agreements.
The fact that the UK had a lot of people working part time balanced out the fact that a lot of people were working long hours when average working hours were being calculated, he said.
Longer hours does not however necessarily lead to greater productivity.
Statistics from EIRO/Eurostat show that French workers put in 5.6 fewer hours a week than those in the UK, yet have much higher productivity levels. And while UK productivity, measured by GDP per worker, has improved, it is 13% behind the average output of other G7 countries.
The TUC's general secretary Brendan Barber says: "We are working just about the longest hours in Europe and yet our productivity performance is dismal." 'Limited enforcement'
No matter what sector you work in, it will be difficult to enforce a change in the directive.
Agreement between unions, business and the government is needed before change can be implemented, says David Coats, associate director at the Work Foundation.
"Changes in the law will not change patterns of working overnight. People can't be told tomorrow they can't work more than 48 hours a week.
"The real weakness of the EU proposal is that it does not address whether people will have real choice over their hours, and whether they have enough clout with their employers.
"If there is a strong workplace culture encouraging long hours, it may be difficult to go against that." And Jonathan Maude, employment specialist at Manches law firm, said: "The real Achilles heel of the directive is - where is the enforcement going to come from?"
He doubts inspectors will have the time to check on hours worked and believes that employee grievances rarely centre on the number of hours worked.
"Most employers are very flexible if it comes to working hours, and if staff put in extra hours during the week, that is recognised and they are given time off where the opportunity arises."
By Bill Wilson
BBC News Online business reporter BBC News