Britain is set for a showdown with the European Commission over the working hours of Britain's employees.

The commission has taken up UK trade union complaints that the EU's working time directive has not been fully implemented.

It has begun legal proceedings against the UK and has given ministers until May 21 to respond - a move that has angered business leaders.

The action was brought about after the manufacturing union Amicus said the directive was being "unlawfully and inadequately" implemented.

The EU has held up three complaints from the union - the failure by firms to enforce holiday rights, excluding night shifts from the hours worked and failing to record hours worked voluntarily.

If Britain fails to comply the Commission could take the UK to the European Court of Justice. The whole process is likely to take up to a year.

Britain has always set aside the directive arguing that employees should be allowed to voluntarily work longer hours in order to take advantage of overtime money.

The hours worked by junior doctors has often been cited as an example of working practice where essential services would not be delivered if minimum hours rules were observed.

Roger Lyons, Amicus general secretary, said it was time for the government to bring UK law into line with EU legislation.

"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 enjoyed throughout the rest of Europe," he said.

The action brought an angry response from business leaders who said the current balance allowed flexibility for both employers and their workers.

The CBI said implementation would be a bureaucratic nightmare and urged the government to defend the UK's freedom.

"Some trade unionists seem totally uninterested in flexibility and choice. They only want to control and nanny how long people can work," said John Cridland, CBI deputy director-general.