Vijay Bahuguna, elected recently to the Lok Sabha from the Tehri Garhwal constituency in Uttarakhand, took oath on Friday.
The Congress member won the by-poll defeating BJP's Manujendra Shah.
The death of Shah's father Manvendra Shah had led to the bye-election.
Vijay is the son of the late H N Bahuguna, a former UP Chief Minister.
