Which prime minister appointed the Sarkaria Commission?

The Sarkaria Commission was appointed by the then Prime Minister Smt. Indira Gandhi. It is a three member commission under the chairmanship of Justice R.S. Sarkaria to review the question of centre state relations. The commission submitted its report to the then prime minister Rajiv Gandhi on 27 October 1987.Its charter was to examine the relationship and balance of power between state and central governments in the country and suggest changes within the framework of the Constitution of India. 

Further Reading:

• Different Commissions and their Recommendations
• Views of Sarkaria Commission