Delay in promotion due to changes in recruitment rules of central govt employees

In this scenario, you might consider challenging the denial of promotion through a legal approach. You could draft a representation to your office. As per legal principles in India, retrospective changes in service conditions affecting vested rights are generally disallowed unless expressly mentioned in the legislation. Your eligibility, having met the conditions before the amendment's effective date, may establish your right to promotion.

You could refer Article 311 of the Constitution, which protects government employees' rights and prohibits arbitrary action. Also, the Supreme Court in Umesh Kumar Nagpal vs. State of Haryana case held that changes in service conditions detrimental to employees' rights can't apply retrospectively without express provisions.

Highlight your fulfillment of the prior conditions for promotion by June 2023, emphasizing your legitimate expectation for promotion. Request consideration based on vested rights accrued before the amendment's effective date. Seek relief by explaining the delay in the panel's formation and assert your right to promotion based on existing rules at the time of your eligibility.

Consulting legal counsel or employee unions may further strengthen your case to assert your legitimate entitlement to the promotion.

If your name do not reflect in the list for promotion in the promotion panel;, then you may first make a representation in writing to the competent authority through proper channel .

If your grievances remain not redressed, you can approach CAT with an applicaiton venting out your grievances and seek remedy and relief.

Agreeing with above views, i will add :-

You said you have completed the qualifying service for 3 years in june 2023

but

1. whether vacancy existed in Jue 2023?
2. whether you were the sernior most claimant for the post?

this information is absolutely important before advising any further course of action.