Those opposing the reservation in promotion told the five-judge constitution bench headed by the Chief Justice Dipak Misra that there cannot be reservation without balance.

"The state is reposed with the responsibility to strike a balance and not just enforce reservation," pleaded senior counsel Shanti Bhushan and Rajeev Dhavan on behalf of the respondents opposing the Centre's plea for reconsideration of 2006 judgment by which top court had laid down the criteria for reservation in promotion for SC/ST.

Spelling out the foundational features of the 2006 Nagaraj judgment, Dhavan said that the creamy layer was a principle of equality and equality has to be substantive and not just formal.

He told the bench that Nagaraj judgment, for ensuring that equality as basic structure is not violated, had laid the pre-condition of compelling reasons -- backwardness, inadequacy of representation -- and overall administrative efficiency which the government has to satisfy before embarking for reservation in promotion.

Defending the Nagaraj judgment, Dhavan said it can be revisited only if there is foundational defect in it.

"There was no fatal flaw in Nagaraj judgment," Dhavan told the constitution bench.

Earlier, arguing for another respondent, senior counsel Shanti Bhushan said that reservation is for a class of people who are backward and not for an individual in a cadre in government job.

Finding no infirmity with the reservation at the entry stage, Bhushan said that once a person is collector, Income Tax officer or holding any such or equivalent position then any reservation in promotion would be for an individual, as at that level no one is backward.

Reservation in government jobs at entry point would be for the "class of backward people", but subsequent intra-cadre reservation would be for an individual, as having occupied a position in government service he cannot be described as backward.

Earlier, seeking reconsideration of the top court decision in Nagaraj judgement, senior counsel Indira Jaising said that the validity of the constitutional provisions could not be tested on the grounds of "compelling reasons -- backwardness, inadequacy of representation and overall administrative efficiency".

Contending that there could not be any "quantitative exclusion" of SC/ST, Jaising said that it was only the "100-point roster system that would ensure that nobody (in reserved category) would exceed the ceiling limit of quota".

Jaising appeared for an apex body of SC/ST employees serving in the government.

By its 2006 judgment, the top court had upheld the validity of Constitution's 85th Amendment by which Article 16 (4A) -- providing for reservation in promotion with consequential seniority" was inserted in the Constitution.

The reservation in promotion was to come into effect retrospectively from June 17, 1995.

The judgment that was pronounced on October 19, 2006, had said: "... State will have to show in each case the existence of compelling reasons, namely backwardness, inadequacy of representation and overall administrative efficiency, before making provision for reservation in promotion."

Senior counsel Dhavan will resume his arguments on August 29 - the next date of hearing.