The precise wording in Appendix 6 to Part-FCL is: "The ATO shall ensure that the applicant for a multi-engine IR(A) course who has not held a multi-engine aeroplane class or type rating has received the multi-engine training specified in Subpart H prior to commencing the flight training for the IR(A) course."
Thus there is no requirement to have passed the MEP class rating skill test and the CAA advice quoted by Mach 1.1 was incorrect (not for the first time). The requirement has not changed since it was first introduced at Amendment 4 to JAR-FCL-1.