Lawyers for Denis O'Brien have confirmed to the High Court that he is appealing the court's refusal to order a company to disclose documents revealing the identity of a client who commissioned a dossier about the businessman.

Mr O'Brien has taken legal proceedings against Red Flag Consulting, alleging the material in the dossier is defamatory and designed to harm him.

He asked the court to order Red Flag to disclose documents revealing the identity of the client. However the High Court refused and today awarded the costs of that application against Mr O'Brien.

The judge said the hearing could have been avoided if Red Flag's reasonable offers concerning the discovery of documents had been taken up by Mr O'Brien.

He rejected an argument by Mr O'Brien's lawyers that costs issues should await the outcome of Mr O'Brien's main case against Red Flag.

The judge said there was no good reason not to give Red Flag the costs of the application, but he put a stay on the order pending an appeal by Mr O'Brien.