Europe's broker-dealers have highlighted trading transparency as one of their key concerns in the review of the Market in Financial Instruments Directive, ahead of a critical European Parliament vote that will help to finalise many of the details of the closely-watched reforms.

Nearly 80% of broker-dealers responding to a survey by PricewaterhouseCoopers said that the increased requirements for pre and post-trade transparency across a range of asset classes outlined in the Mifid review is their greatest "concern".