Prime Minister Narendra Modi’s chief rival Rahul Gandhi was appointed on Tuesday to lead India’s opposition in parliament, a key post that has been vacant for a decade.

Congress party general secretary KC Venugopal said Gandhi would be “a bold voice for the common people of India” and ensure the government “is held firmly accountable at all times”, he told reporters in a statement.

Venugopal said Congress party chairperson Sonia Gandhi, Rahul’s mother, had written to the parliament temporary speaker informing him he “is appointed as the Leader of Opposition in the Lok Sabha”, India’s lower house.

Congress leader defied analysts’ expectations and exit polls to help his Congress party nearly double its parliamentary numbers, its best result since Modi swept to power in 2014. Gandhi is the scion of the dynasty that dominated Indian politics for decades and is the son, grandson, and great-grandson of former prime ministers, beginning with independence leader Jawaharlal Nehru.

Parliamentary regulations require the opposition leader to come from a party that commands at least 10% of the lawmakers in the 543-seat lower house. The post has been vacant for 10 years because two dismal election results for Congress – once India’s dominant party – left it short of that threshold.

Modi and his Hindu-nationalist BJP ruled outright for the past decade but failed to repeat its previous two landslide wins this time, despite widespread expectations of another easy triumph.

Earlier on Tuesday, Gandhi took the oath in parliament as a newly-elected lawmaker. “To protect the Constitution is the duty of every patriotic Indian,” he said shortly after in a statement. “We will fulfil this duty in full measure.”

Gandhi is one of several top opposition figures to face criminal proceedings in cases they claim are politically driven by Modi’s government.

He was sentenced to two years imprisonment last year in 2023 in a separate case in Gujarat but was not jailed after appealing with India’s top court. The sentence did, however, force his brief disqualification from parliament until the Supreme Court suspended his conviction.