At any time before the matter is submitted for decision the agency may file or permit the filing of an amended or supplemental accusation. All parties shall be notified of the filing. If the amended or supplemental accusation presents new charges the agency shall give the respondent a reasonable opportunity to prepare a defense to it, but the respondent is not entitled to file a further pleading unless the agency in its discretion so orders. New charges are considered controverted. Objections to the amended or supplemental accusation may be made orally and shall be noted in the record.