A FIRM Of insurance brokers began a defamation action against the Irish Brokers Association before Mr Justice Kinlen and a jury in the High Court yesterday. However, following submissions in the absence of the jury, it was discharged and the case was put back to the next court list for the fixing of dates. The plaintiffs claimed they were defamed in letters sent by the IBA to a number of insurance companies in April 1992. The defence denied the claims.