A division bench of Supreme Court held as follows,

From Para 15,

15. Before discussing the fact proposition, we would notice the principle of law as laid down by this Court. It is settled law that non-entertainment of petitions under writ jurisdiction by the High Court when an efficacious alternative remedy is available is a rule of self-imposed limitation. It is essentially a rule of policy, convenience and discretion rather than a rule of law. Undoubtedly, it is within the discretion of the High Court to grant relief under Article 226 despite the existence of an alternative remedy. However, the High Court must not interfere if there is an adequate efficacious alternative remedy available to the petitioner and he has approached the High Court without availing the same unless he has made out an exceptional case warranting such interference or there exist sufficient grounds to invoke the extraordinary jurisdiction under Article 226. (See: State of U.P. vs. Mohammad Nooh, AIR 1958 SC 86; Titaghur Paper Mills Co. Ltd. vs. State of Orissa, (1983) 2 SCC 433; Harbanslal Sahnia vs. Indian Oil Corpn.
Ltd., (2003) 2 SCC 107; State of H.P. vs. Gujarat Ambuja Cement Ltd., (2005) 6 SCC 499).
16. The Constitution Benches of this Court in K.S. Rashid and Sons vs. Income Tax Investigation Commission, AIR 1954 SC 207; Sangram Singh vs. Election Tribunal, Kotah, AIR 1955 SC 425; Union of India vs. T.R. Varma, AIR 1957 SC 882; State of U.P. vs. Mohd. Nooh, AIR 1958 SC 86 and K.S. Venkataraman and Co. (P) Ltd. vs. State of Madras, AIR 1966 SC 1089 have held that though Article 226 confers a very wide powers in the matter of issuing writs on the High Court, the remedy of writ absolutely discretionary in character. If the High Court is satisfied that the aggrieved party can have an adequate or suitable relief elsewhere, it can refuse to exercise its jurisdiction. The Court, in extraordinary circumstances, may exercise the power if it comes to the conclusion that there has been a breach of principles of natural justice or procedure required for decision has not been adopted.
(See: N.T. Veluswami Thevar vs. G. Raja Nainar, AIR 1959 SC 422; Municipal Council, Khurai vs. Kamal Kumar, (1965) 2 SCR 653; Siliguri Municipality vs. Amalendu Das, (1984) 2 SCC 436; S.T. Muthusami vs. K. Natarajan, (1988) 1 SCC 572; Rajasthan SRTC vs. Krishna Kant, (1995) 5 SCC 75; Kerala SEB vs. Kurien E. Kalathil, (2000) 6 SCC 293; A. Venkatasubbiah Naidu vs. S. Chellappan, (2000) 7 SCC 695; L.L. Sudhakar Reddy vs. State of A.P., (2001) 6 SCC 634; Shri Sant Sadguru Janardan Swami (Moingiri Maharaj) Sahakari Dugdha Utpadak Sanstha vs. State of Maharashtra, (2001) 8 SCC 509; Pratap Singh vs. State of Haryana, (2002) 7 SCC 484 and GKN Driveshafts (India) Ltd. vs. ITO, (2003) 1 SCC 72).

From Para 19,

19. Thus, while it can be said that this Court has recognized some exceptions to the rule of alternative remedy, i.e., where the statutory authority has not acted in accordance with the provisions of the enactment in question, or in defiance of the fundamental principles of judicial procedure, or has resorted to invoke the provisions which are repealed, or when an order has been passed in total violation of the principles of natural justice, the proposition laid down in Thansingh Nathmal case, Titagarh Paper Mills case and other similar judgments that the High Court will not entertain a petition under Article 226 of the Constitution if an effective alternative remedy is available to the aggrieved person or the statute under which the action complained of has been taken itself contains a mechanism for redressal of grievance still holds the field. Therefore, when a statutory forum is created by law for redressal of grievances, a writ petition should not be entertained ignoring the statutory dispensation.

Citations : [2013 AD SC 8 620], [2013 CTR SC 261 113], [2013 ITR SC 357], [2013 JLJR 4 35], [2013 JT SC 11 387], [2013 PLJR 4 179], [2013 SCALE 10 326], [2014 SCC 1 603], [2013 TAXMAN SC 217 143], [2013 SCC ONLINE SC 717], [2013 TAXMANNCOM SC 36]

Other Sources :

https://indiankanoon.org/doc/51987756/

https://www.casemine.com/judgement/in/5609af2ce4b0149711415ba2