Speaker of Punjab Vidhan Sabha, Charanjit Singh Atwal administered the oath of office and secrecy to Jain in his chamber, a Vidhan Sabha spokesman said here.
Besides Atwal and Jain, others present on the occasion include Chief Minister Parkash Singh Badal and Revenue Minister Bikram Singh Majithia.
Jain had defeated Vijay Sathi of Congress at the Moga by-poll by a margin of over 17,000 votes. The by-poll was necessitated after Jain deserted the Congress to join SAD. This was Jain's third consecutive win on Moga seat.