Business said on Thursday it would resist any European Commission bid to make it harder for firms to break working time limits laid down by the bloc's laws.
Influential business lobby group UNICE said it also wanted the so-called working time directive to be more flexible in calculating the average weekly working time and to distinguish between time worked and time spent resting at the workplace.
Its wish list was set out in a position paper submitted to the Commission, which is asking for feedback before end-March on whether to revise a directive that says employees cannot be forced to work more than an average of 48 hours per week.
The European Parliament and British trade unionists have already called on the EU executive to narrow the scope of the opt-out which allows firms to get around the working time rules. This opt-out is used most widely in Britain, Brussels says.
"We would oppose a directive that would suppress this (opt out) right and ask that the right (of opt out), either by individual or collective agreement, is maintained," said Therese de Liedekerke, director of social affairs at UNICE.
"The more flexibility you have in the directive, the more favourable the conditions for employment creation."
One way firms get around the rules is by asking prospective employees to sign the opt-out at the same time as their employment contract, a practice which effectively compromises a worker's freedom of choice, the Commission has said in the past.