The ambitious plan to create a single, pan-European market for financial services hit a fresh obstacle yesterday, after it emerged that all but three of the European Union's 27 member states could face legal action for failing to implement the rules that form the basis of the industry shake-up.

Charlie McCreevy, the EU internal market commissioner, wrote to 24 national governments to express his "deep concern" about the delayed introduction of the markets in financial instruments directive, or Mifid.