A study by Kronos found 50% of employers think the removal of the opt-out will have an adverse impact on their company's profits.
Currently 90% of employers have staff who work more than 48 hours per week, but the EU has voted to ban this. Less than a third (30%) plan to make any changes once the opt-out is removed but 45% are planning more flexible working arrangements, 35% will be recruiting additional staff and training existing employees.
But 45% of employers think it will be difficult to manage the new regulations under their existing systems to monitor employees' working hours - two in 10 think it will take in excess of 10 hours over a pay period.
Keith Stratham, managing director of Kronos, said: "In the current climate, any negative effect on productivity and customer service will not be welcome by employers."
