The British Chambers of Commerce have called new plans from the European Parliament to extend maternity leave from six to 20 weeks "unaffordable".
The BCC said that an impact assessment of the proposed Pregnant Workers Directive, carried out on behalf of the EU Parliament, found that the cost to Britain would be £2.5 billion per year should the rules come into force.
The assessment only looked at the impact on ten out of the 27 EU states meaning that when MEPs vote on the proposal in October they will "not be able to make a fully informed decision," the BCC said.
Over a 19 year period the BCC said that the cost of the proposals would be 121.18 billion euros to the ten states examined. Of that cost around 47 per cent would fall on Britain.
Kieran O'Keeffe, Head of European Affairs at the British Chambers of Commerce, said, "This directive should be about setting minimum EU standards for the health and safety of pregnant workers - not adding new payroll costs for overburdened companies and national social security systems.
"These figures confirm that the Parliament's proposals are completely unaffordable as governments across the EU seek to deal with budget deficits and the aftermath of recession.
"The Commission's original proposal to extend maternity leave to 18 weeks, but with individual member states allowed to decide the level of pay, is a better, more affordable option."