After the entry of a Board order directing payment of backpay, or the entry of a court decree enforcing such order, if it appears to the Regional Director that a controversy exists between the Board and a respondent which cannot be resolved without a formal proceeding, the Regional Director may issue and serve on all parties a backpay specification accompanied by a notice of hearing or a notice of hearing without a specification. The respondent shall, within twenty (20) days after the service of a backpay specification accompanied by a notice of hearing, file an answer thereto in accordance with § 1423.13 with the Regional Director issuing such specification. No answer need be filed by the respondent to a notice of hearing issued without a specification. After the issuance of a notice of hearing, with or without a backpay specification, the procedures provided in §§ 1423.14 to 1423.29, inclusive, shall be followed insofar as applicable.