The UK Offshore Operators Association, which represents oil companies including BP and Shell, said it believed it had lost a long-running campaign to maintain the exclusion for employees working on offshore rigs and platforms.
Any move to extend the law will be likely to damage further relations between the commission and the UK government, which has pledged to fight the directive following a recent setback for ministers in the European Court of Justice.
The legislation, which came into effect across the EU last Saturday, limits employees to a maximum 48-hour week and imposes controls on rest periods and night shifts.
A draft white paper examining excluded industries, prepared by the office the social affairs commissioner, Padraig Flynn, is thought to have come down in favour of extending the directive to the offshore oil and gas sector.
Andrew Searle, from the Offshore Operators Association, said: "We are absolutely confident and adamant that our industry has lost its exclusion. We've been lobbying the European Commission for 18 months and we are sure there is no reference to our industry maintaining its exclusion from the legislation. This is of enormous concern to us."
The offshore oil industry, which comes under the category of work at sea, was one of eight sectors excluded from the original European law on the grounds that employees involved worked unusual shift patterns. The directive has been treated as a health and safety measure by the EC and is therefore not covered by the British opt-out from legislation in the Social Chapter of the Maastricht Treaty.
Most offshore employees work 12-hour shifts every day for two weeks, followed by two weeks' leave at home. Though over a four-month period, total hours would generally be within the 48 stipulated by the directive, the industry is more concerned with other rules governing shift breaks and night work. These guarantee a minimum rest period of 11 consecutive hours in each 24-hour period and restrict night shifts to an average of eight hours.
The Offshore Operators Association said this would add millions of pounds of costs to the pounds 1.5bn spent annually on North Sea projects.
However, a spokeswoman for Mr Flynn denied that any final decisions had been taken about industries which could lose their exclusions.
"Nothing has crystallised yet and before we decide, we will be discussing matters with the various cabinets in Brussels. I would describe the oil companies' response as over-reaction," she said.
The final version of the white paper is due to be published in the new year.Reuse content