http://www.legislation.gov.uk/ukpga/1986/44/section/23DGas Act 1986Gas Act 19861986-07-25texttext/xmlenStatute Law Database2026-08-10Expert Participation2025-11-13 Gas Act 1986s. 23D(2)(b)Energy Act 2013s. 138(4)(c)(i)s. 156(1)Gas Act 1986s. 23D(2)(c)Energy Act 2013s. 138(4)(c)(ii)s. 156(1)Gas Act 1986s. 23D(2)(d) and wordEnergy Act 2013s. 138(4)(c)(iii)s. 156(1)Gas Act 1986s. 41E(6)(d) and wordEnergy Act 2013s. 138(4)(f)(ii)s. 156(1)Gas Act 1986s. 27(1ZA)(aa)The Competition (Amendment etc.) (EU Exit) (No. 2) Regulations 2019 (expired—not approved)reg. 17reg. 1(1)Gas Act 1986s. 5(1)(ca)Energy Act 2023s. 168(2)(b)s. 334(1)Gas Act 1986s. 5(10A)Energy Act 2023s. 168(2)(c)s. 334(1)Gas Act 1986s. 15ACompetition and Service (Utilities) Act 1992s. 17s. 56(2) Part I23D1This section applies to every appeal brought under section 23B.2In determining an appeal the CMA must have regard, to the same extent as is required of the Authority, to the matters to which the Authority must have regard—ain the carrying out of its principal objective under section 4AA;bin the performance of its duties under that section; andcin the performance of its duties under sections 4AB and 4A.3In determining the appeal the CMA —amay have regard to any matter to which the Authority was not able to have regard in relation to the decision which is the subject of the appeal; butbmust not, in the exercise of that power, have regard to any matter to which the Authority would not have been entitled to have regard in reaching its decision had it had the opportunity of doing so.4The CMA may allow the appeal only to the extent that it is satisfied that the decision appealed against was wrong on one or more of the following grounds—athat the Authority failed properly to have regard to any matter mentioned in subsection (2);bthat the Authority failed to give the appropriate weight to any matter mentioned in subsection (2);cthat the decision was based, wholly or partly, on an error of fact;dthat the modifications fail to achieve, in whole or in part, the effect stated by the Authority by virtue of section 23(7)(b);ethat the decision was wrong in law.5To the extent that the CMA does not allow the appeal, it must confirm the decision appealed against.Pt. I: definition of "public gas supplier" applied (E.W.) (1.12.1991) by Water Resources Act 1991 (c. 57, SIF 130), ss. 208(3)(b), 225(2) (with ss. 16(6), 179, 222(3), Sch. 22 para. 1, Sch. 23 para. 6)Pt. I: definition of "public gas supplier" applied (E.W.) (1.12.1991) by Water Resources Act 1991 (c. 57, SIF 130), ss. 178, 225(2), Sch. 22 para. 1(4)(e) (with ss. 16(6), 179, 222(3), Sch. 22 para. 1, Sch. 23 para. 6)Pt. I applied (1.3.1996) by 1995 c. 45, s. 6(7); S.I. 1996/218, art. 2Pt. I applied (1.3.1996) by 1995 c. 45, s. 16(1), Sch. 4 para. 1; S.I. 1996/218, art. 2Word in s. 23D heading substituted (1.4.2014) by Enterprise and Regulatory Reform Act 2013 (c. 24), s. 103(3), Sch. 6 para. 18(3); S.I. 2014/416, art. 2(1)(d) (with Sch.)Word in s. 23D(2)-(5) substituted (1.4.2014) by Enterprise and Regulatory Reform Act 2013 (c. 24), s. 103(3), Sch. 6 para. 18(2); S.I. 2014/416, art. 2(1)(d) (with Sch.)Ss. 23B-23G and cross-heading inserted (10.11.2011) by The Electricity and Gas (Internal Markets) Regulations 2011 (S.I. 2011/2704), regs. 1(1), 41(7) (with reg. 42)