With uncertainty looming large over the quota regime, the Centre will have to pass a stiff test on Monday in the Supreme Court, which is likely to hear its plea for early vacation of the stay on the 27 per cent reservation for OBCs in elite educational institutions.

At the outset, the government has the daunting task of satisfying the court that its application for clarification and vacation of the March 29 stay is not a petition for a review of the interim order.

The Centre's plea will come up for hearing before a bench comprising Justices Arijit Pasayat and L S Panta, which had stayed the implementation of certain provisions of the Central Educational Institutions (Reservation in Admissions) Act enabling a quota in institutions like IIMs, IITs and AIIMS.

When the Centre mentioned its application on April 18 for an early hearing before the same bench, it was told that it first had to satisfy the maintainability of the petition as its essence appeared to be seeking a review of the March 29 order.

The Centre also received flak from the apex court as its application said the March 29 order was in the nature of advice to the Central government.

Solicitor General G E Vahanvati had said that the implementation of the Act from the coming academic session would not come in the way of general category candidates.

After the case was posted for April 23, the IIMs decided to keep on hold admissions to their postgraduate programme for the coming academic year till the apex court decided on the issue.

The move came shortly after the Central government asked the six IIMs to keep in abeyance their admission process pending the hearing in the apex court.

During an earlier hearing, Vahanvati had said he had instructions to give an undertaking to the court that there would be no reduction of seats available in the general category in each Central educational institution during the immediately preceding academic session of 2006.

He had said the policy of reservation will be implemented simultaneously and limited to the expansion in capacity of such institutions.

Students belonging to OBCs (and the proportionate increase of seats for Scheduled Castes and Scheduled Tribes) shall be admitted only against the increased seats so that there is no adverse effect on the number of seats in general category, Vahanvati said.

However, the bench said the same point was made by Additional Solicitor Gopal Subramanium before it passed the interim order. The Centre, in its modification application, sought the setting up of a five-member Constitution bench to hear the matter and opposed the exclusion of the 'creamy layer' from the benefits of reservation.

The government maintained that the decision of the nine-judge Constitution bench in the Indira Sawhney case (Mandal Case) upholding reservation for OBCs 'is binding on all concerned, including the petitioners, the government as well as a two-member bench of this honourable court.'

It has also contended that the 1931 census was not the basis for identifying OBCs.