The European Commission has dropped a plan to force firms to give 40 percent of non-executive board positions to women in favour of a less drastic obligation to favour female candidates where they are equally qualified, an EU source said on Tuesday.The quota proposal had run into opposition from a number of countries, led by Britain, and from large firms.

Commission lawyers said it was "problematic" for the European Union to impose strict quotas, though it could instruct companies on how to hit quotas.

The new proposal would now oblige companies with more than 250 staff to favour "the underrepresented sex" from 2016 onward in order to achieve 40 percent female representation, the source said, speaking on condition of anonymity.

Member countries would have the power to determine and impose sanctions on firms that did not obey the rule.

The 27 European Commissioners are scheduled to vote on the proposal on Wednesday. If a majority approve, the plan will then be voted on by the European Parliament and the 27 member countries.