12.—(1) Subject to paragraph (2), for the purpose of seeking offers in relation to a proposed public contract, a contracting authority shall use—
(a)the open procedure in accordance with regulation 15; or
(b)the restricted procedure in accordance with regulation 16;
in all circumstances, except where it may use—
(i)the negotiated procedure in accordance with regulation 17 in the circumstances referred to in regulations 13 and 14; or
(ii)the competitive dialogue procedure in accordance with regulation 18.
(2) Paragraph (1) does not apply in the case of a subsidised housing scheme works contract which is subject to regulation 35.