Attempts are under way to tighten up the EU Working Time Directive, which governs the hours employees can be asked to work.
The European Commission proposed a set of changes in 2004, followed by the European Parliament in 2005.
However, nothing can happen until the EU's 25 member states agree on the changes they would like to see - and they cannot agree.
At the heart of the arguments is a controversial opt-out, which allows employees in the UK and some other member states to work more than the generally adopted maximum of 48 hours per week.
What is the working time directive?
The directive is a European Union initiative designed to protect workers from exploitation by employers.
It lays down regulations on matters such as how long employees work, how many breaks they have, and how much holiday they are entitled to.
One of its main goals is to ensure that no employee in the European Union is obliged to work more than an average of 48 hours a week.
When did it become law and why is it in the news now?
It was first adopted at EU-level in 1993, though the UK did not implement it until 1998.
It's in the news now because the European Commission proposed some changes to the directive in 2004.
More recently, the EU's member states and the European Parliament have been responding to these proposals.
The Parliament voted on a set of proposed amendments in May 2005. Member states have been unable to agree a common position.
What are the most contentious issues?
(1) The opt-out. This is a measure which allows workers to agree to opt out of the 48-hour week. Employers in a number of states make use of the opt-out, but it is most widely used in the UK and Malta.
(2) Time spent on call. The European Court of Justice has ruled that on-call time should count as working time, which has left many countries struggling to keep doctors' average weekly working hours below the agreed limit.
What will happen to the opt-out?
The European Commission is content to allow the opt-out to continue, though it has suggested measures that would make it harder for employers to press staff into working more than 48 hours against their will.
However, some countries want the opt-out to be phased out, as does the European Parliament.
Other states, in particular the UK, want it to continue. They argue that labour market flexibility helps reduce unemployment.
The UK does not have a veto in this area, so it could be outvoted, but so far support from Germany and Poland has helped it avoid this fate.
What about time spent on call?
The European Commission has proposed making a distinction between "active" and "inactive" time on duty. Inactive time on duty would not count as working time.
Most countries agree with this, but the European Parliament does not. The parliament does say, however, that inactive time could be calculated differently.
What happens next?
If the member states ever reach agreement, the law will go back to the European Parliament for a second reading.
It could take a while for the EU member states and the parliament to agree on a text. If they cannot agree, the legislation will fail.
What else does the Working Time Directive do?
Among other things, it guarantees at least four weeks' paid annual leave; a minimum period of 11 hours' rest every 24 hours, and one day a week; a rest break if the working day is longer than six hours; a maximum of eight hours' night work, on average, in each 24; and health assessments for night workers.
Are any categories of workers excluded?
To begin with the directive did not apply to air, rail, road, sea, inland waterway and lake transport, sea fishing, offshore work and the activities of doctors in training. However nearly all are now covered either by amendments to the directive (adopted in 2000), or by separate directives on road, sea and air transport.
Restrictions on the weekly working hours of doctors in training are being phased in as follows: 58 hours from 1 August 2004 to 31 July 2007; 56 hours from 1 August 2007 to 31 July 2009; 48 hours from 1 August 2009.
How many hours do employees work, in practice?
According to the European Trade Union Confederation, full-time workers in the UK work for an average of 44 hours, compared with about 40 hours in the 14 other longstanding EU member states.
The ETUC says about 16% of the UK labour force works more than 48 hours per week, and that two-thirds are unaware of the 48-hour limit.
France has introduced a 35-hour working week.