(1) A presiding hearing officer may not participate in or initiate any ex parte consultation, as defined in (2), on the merits of a matter with any party or the department.

(2) "Ex parte communication" means the communication with the presiding hearing officer by any person having interest in the outcome of the contested case proceeding regarding the merits of the case without notice or argument by any person adversely interested. A hearing officer may engage in communication concerning administrative or procedural matters where necessary under the circumstances and which does not adversely affect the substantial rights of a party.