Average working hours per week:

UK: 43.6 Greece: 40.8 Spain: 40.6 Portugal: 40.6 Austria: 40.2 Sweden: 40.1 Germany: 40.1 Ireland: 40 Luxembourg: 39.7 France: 39.6 Finland: 39.3 Netherlands: 39 Denmark : 38.9 Italy: 38.5 Belgium : 38.4 Source: Workplace Employee Relations Survey 1998

The proceedings followed a complaint from Amicus, Britain's second biggest union, that the UK government had "unlawfully and inadequately" implemented measures limiting the working week to 48 hours.

Serious concerns were also raised about British employees' rights to shift breaks and holidays.

Business anger

The commission's decision was welcomed by Amicus general secretary Roger Lyons as a "historic victory for British workers".

But employers' organisations warned that fully implementing measures within the EU's working time directive would erode the competitiveness of UK firms.

"Business will be deeply concerned about the Amicus action," said John Cridland, deputy director general of the Confederation of British Industry.

Britons currently work 43.6 hours a week, compared with a European average of 40.3 hours.

Opt out clause

Brussels is believed to have given the government two months to comply fully with the working time directive, which Tony Blair's administration signed up to soon after coming to power in 1997.

Some professions are exempt from the rule

The directive says employees cannot be forced to work more than 48 hours a week, although certain professions, including some healthcare workers and the media, are exempted.

When the move was agreed, the UK obtained a special dispensation to allow people to volunteer to work longer than 48 hours if they wished.

But Amicus said the UK Government was not doing enough to enforce the directive and a full investigation into the complaint is now under way.

The government said it was considering the complaint before responding to the "threat" of so-called infringement proceedings, which could see the government taken to the European Court of Justice, in Luxembourg.

BBC business correspondent Hugh Pym says that currently, employers are not obliged by the government to ensure that staff have breaks in the working day or take holidays.

Also, hours worked as overtime on a night shift are not included in the 48-hour count, Mr Pym said.

Pros and cons

Amicus's Roger Lyons said: "Britons work the longest hours in Europe.

"This decision will cut excessive working time considerably, slash stress and bring us closer to the level of working hours already enjoyed throughout the rest of Europe."

But industry groups warned that implementing stricter working hours guideline would limit company flexibility, and erode the UK's advantage as a business base.

"Some trade unionists seem totally uninterested in flexibility and choice," the CBI's John Cridland said

"They only want to control and nanny how long people can work."

Worker output 'too low'

Ian Fletcher, head of policy at British Chambers of Commerce, said the longer hours worked in the UK were a symptom of lower productivity.

"What business and trades unions should be trying to do is raise productivity, so that British workers can enjoy the same standards of living for less hours worked," Mr Fletcher said.

He added: "Knowing some union leaders, we doubt whether they work less than 48 hours a week or indeed take all their holiday entitlement.

"Why should other individuals not have the same choice?"

Unpaid labour

The TUC estimates that more than 4 million people regularly work more than 48 hours a week.

An average employee, it claims, clocks up unpaid labour worth �5,000 every year.

A survey carried out at the end of last year by Essex University suggested that more than a third of employees in the UK felt overworked.