JUDGMENT Venkatachala, J. - Leave granted. 2. This appeal raises the questions as to inter se seniority between Ramvir Singh the appellant and D N Gupta respondent 4 in the cadre of Medico Social Workers of Dr Ram Manohar Lohia Hospital, New Delhi (for short the Hospital) and the validity of the appointment of respondent 4 in the higher cadre post of Medico Social Service Officer of the same Hospital on ad hoc basis at the first instance and on permanent basis sub-sequently. It would be convenient to refer to the material facts which bear on the said questions at the very outset. 3. Three posts in the cadre of Medico Social Workers came to be created in the Hospital by an Order dated August 24, 1978 by the Ministry of Health and Family Welfare of the Central Government. The Hospital authorities sought to fill-up those posts by candidates sponsored by the Employment Exchange as also the in-service candidates of the Hospital, according to their performance at interview. The Hospital authorities held the interview for the said candidates on February 1, 1979 and prepared a select list of three candidates required to fill up the said three posts of Medico Social Workers. The appellant, the candidate sponsored by the Employment Exchange while was selected and placed in that select list, respondent-4, an in-service candidate was not so selected and hence did not find any place therein. Although, all the three candidates, who found places in the select list were given appointment orders for filling-up the said posts of Medico Social Workers, only the appellant and another P G Raduppa, joined two of those posts on September 25, 1979. The other post remaining vacant, due to one of the appointees not joining it, was re-advertised on January 10, 1980 inviting applications from eligible candidates Respondent 4, who was not selected to that post earlier, having applied for it came to be appointed therein and joined it on April 11, 1980. Four years later, when a provisional seniority list dated July 25, 1984 of the appointees in the cadre of Medico Social Workers in the Hospital was prepared, the seniority of the appellant (Sh. Ramvir Singh) against respondent 4 (Sh. D.N Gupta) in that cadre was maintained as becomes obvious from the following excerpt of that list : Sl. No. Name Date of entry into Govt. service Date of apptt. Ramvir Singh) against respondent 4 (Sh. D.N Gupta) in that cadre was maintained as becomes obvious from the following excerpt of that list : Sl. No. Name Date of entry into Govt. service Date of apptt. to the present post Date of birth Perm Temp Ad hoc MEDICAL SOCIAL WORKERS 1. Sh. Ramvir Singh 25-9-79 25-9-79 1-3-55 Temp 2. Sh. D. N. Gupta 12-9-66 11-4-80 19-7-43 Temp 3. Miss Indra Bhalla 1-5-82 1-5-82 24-10-45 Purely Ad hoc 4. Respondent 4, three years after the publication of the said provisional seniority list came to request the Hospital authorities on March 15, 1987 seeking preponement of his date of appointment as Medico Social Worker from 11-4-1980 to 25-9-1979 so as to coincide with the date of appointment of the appellant. That request of respondent 4 is granted on June 10, 1989 This development has led the Director General of Health Services, by his Order dated July 9, 1990 to appoint respondent 4 on ad hoc basis in the post of Medico Social Service Officer, an higher cadre post in the Hospital. This ad hoc appointment of respondent 4, a junior to the appellant in the lower cadre, has been challenged by the appellant by an application under section 19 of the Administrative Tribunals Act, 1985 filed before the Central Administrative Tribunal, New Delhi (CAT) with prayers made therein for the quashing of the ad hoc appointment of respondent 4 as Medico Social Service Officer in the Hospital and for issuance of directions to the Hospital authorities and the Union of India, to restore the seniority of the appellant over respondent 4 in the cadre of posts of Medico Social Workers and to consider the claim of the appellant for appointment to the higher cadre post of Medico Social Service Officer in the Hospital in preference to respondent 4. But, that application is dismissed by the CAT by its Order dated July 26, 1991 on its view that by prepoining the date of appointment of respondent 4 as Medico Social Worker to September 25, 1979 the Hospital authorities had corrected an error committed by the Selection Committee in not selecting him on the ground that he did not possess the requisite qualification when he was interviewed on February 1, 1979 along with the appellant, and the subsequest appointment of respondent 4 as Medico Social Service Officer, being an ad hoc appointment was liable to be redone on a regular basis by the Hospital authorities after a revised seniority list was prepared fixing the inter se seniority between the appellant and respondent 4 in the cadre of Medico Social Workers of the Hospital. It is this Order of the CAT which has come to be impugned in this appeal by special leave. However, a letter No. A-12026/7/89-MH dated September 26, 1991 issued by the Directorate General of Health Services shows that he has treated respondent 4 as senior to the appellant in the cadre of Medico Social Workers of the Hospital while an Office Order dated June 23, 1992 issued by the Directorate General of Health Services shows that respondent 4 is promoted as Medico Social Service Officer of the Hospital in a regular temporary capacity from June 22, 1992 until further orders. 5. We shall first deal with the question of inter se seniority between the appellant and respondent 4 in their cadre of Medico Social Workers in the Hospital for that that inter se seniority even if does not form the sole basis for the appointment of either of them in a higher cadre post in the Hospital, the same may constitute a relevant factor for such appointment. 6. 6. When the non-selection of respondent 4 by the Hospital authorities for any of the three newly created posts of Medico Social Workers in the Hospital in the select list prepared by them on the basis of interview held for all the candidates including respondent 4 on February 1, 1979 and the appointment of the appellant and two others made thereon was not questioned by respondent 4, it is difficult to think of the basis on which respondent 4, who was appointed subsequently in one of those posts on a fresh application made by him in that regard, could claim seniority over the appellant, the earlier appointee in one of those posts. Therefore, the Order of the Hospital authorities by which the date of appointment of respondent 4 is preponed from April 11, 1980 to September 25, 1979, the date of appointment of the appellant, so as to enable them to treat the former as senior to the latter in their cadre has to be regarded as an arbitrary one if not a whimsical one. The view taken by the CAT that the preponement of the date of appointment of respondent 4 by the Hospital authorities from April 11, 1980 to September 25, 1979, so as to make him senior to the appellant had the effect of correcting a mistake committed by the Hospital authorities in not selecting respondent 4 to one of the posts of Medico Social Workers on the plea that he did not possess the requisite qualifications, although possessed by him, is erroneous, as such correction even if desired, was impermissible in law, when it is sought so be done ten years after the selection list for the posts had been prepared by the Hospital authorities and when the inclusion of the appellant and the non-selection of respondent 4 in that selection list had remained unquestioned by any mode known to law. Hence, the Hospital authorities were wholly wrong in interfering with the provisional seniority list dated July 25, 1984 relating to the appellant and respondent 4, prepared on the basis of their respective dates of appointment and in making an Order dated September 26, 1991 to the effect that respondent 4 was senior to the appellant. Hence, the Hospital authorities were wholly wrong in interfering with the provisional seniority list dated July 25, 1984 relating to the appellant and respondent 4, prepared on the basis of their respective dates of appointment and in making an Order dated September 26, 1991 to the effect that respondent 4 was senior to the appellant. The CAT was also fully unjustified in upholding the action of the Hospital authorities in the matter of disturbing interse seniority of the appellant and respondent 4 by its Order now under appeal on its view of the authorities having corrected a past mistake while correction by the Hospital authorities of the purported mistake committed by the selection authorities was impermissible by the method they had adopted therefor. 7. The question which remains for our consideration is that relating to the appointment of respondent 4 as Medico Social Service Officer. When this appointment was questioned before the CAT it was an ad-hoc appointment. The CAT has refused to examine the validity of this appointment because of its view that regular appointment to the post of Medico Social Service officer when has to be made regularly, the same could be made on resolution by the Hospital authorities of the dispute between the appellant and respondent 4 as to their inter se seniority in the cadre of Medico Social Workers Unfortunately, what has been done by the Hospital authorities is to make an arbitrary order to the effect that respondent 4 was senior to the appellant in the cadre of Medico Social Workers without hearing the appellant in the matter and appoint respondent 4 on a regular basis in the higher cadre post of Medico Social Service Officer purporting to be on the recommendation of a Departmental Selection Committee. In our view, when the Departmental Selection Committee, as seen from its proceedings produced before us, has decided to select respondent 4 on the basis that respondent 4 at the relevant time held the post of Medico Social Service Officer while the appellant held at the time only the post of Medico Social Worker and further not on the basis that the appellant was senior to respondent 4 as it ought to have been done, such selection gets vitiated making the order dated June 23, 1992 by which respondent 4 is appointed as Medico Social Service Officer on a regular basis, unsustainable. 8. 8. In the result, we allow this appeal, set aside the Order under appeal, allow the application of the appellant made before the CAT, New Delhi and quash the Order No 8-22/78/RMLH/NS/MSW/107I9-22, dated 10-6-1989, the Order No. A-12026/-/89.MH dated 26-9-1991 and the Order No. A-12026/5/92-MH dated 23-6-1992 of the respondents and direct them to refix the inter se seniority of the appellant and respondent 4 in the cadre of Medico Social Workers in the Hospital and consider their cases afresh for appointment to the higher cadre post of Medico Social Service Officer in the Hospital, in the light of this judgment and in accordance with law. No costs. For Citation: 1993 1 UJ (SC) 11C