In case a fiduciary, agent, or other person has the control, receipt, custody, or disposal of, or pays the wages of an employee or group of employees, employed by one or more employers, the Secretary, under regulations prescribed by him, is authorized to designate such fiduciary, agent, or other person to perform such acts as are required of employers under this title and as the Secretary may specify. Except as may be otherwise prescribed by the Secretary, all provisions of law (including penalties) applicable in respect of an employer shall be applicable to a fiduciary, agent, or other person so designated but, except as so provided, the employer for whom such fiduciary, agent, or other person acts shall remain subject to the provisions of law (including penalties) applicable in respect of employers.