(1) On the making of a dispute referral, the energy ombudsman must, as soon as reasonably practicable, give a notice (an investigation notice) to the other party of--
(a) the subject of the relevant dispute; and
(b) details of the referrer that the energy ombudsman considers appropriate; and
(c) when the energy ombudsman proposes to start to investigate the dispute unless the dispute referral has been withdrawn before that time.
(2) However, an investigation notice need not be given if the dispute referral has been withdrawn,
(3) An investigation notice may be oral or written.
(4) However if oral notice is given, the energy ombudsman must confirm it by written notice given within a reasonable period after the giving of the oral notice.
(5) This section is subject to section 22.