Sonia and Rahul Gandhi said they took full responsibility for the Congress party's heavy defeat. Photo: BBC

The party finished with just 44 of the 543 seats and under 20% of the vote in what was its worst ever performance.

The Hindu nationalist Bharatiya Janata Party (BJP) won a landslide win with 282 seats and is set to form a government.

Congress leaders have called for inner party reforms after the defeat.

Congress drew a blank in 12 states. Its attempts to foster democracy within the party by picking candidates in US-style primaries failed to deliver electoral dividends.

Both party chief Sonia Gandhi and her son Rahul Gandhi, Congress' campaign leader, have accepted responsibility for the defeat.

"We did not get the support that we anticipated," Ms Gandhi said.

Reports in the media said Monday's meeting was likely to see criticism of Mr Gandhi's campaign style which "failed to enthuse people".

However, a top aide of Sonia Gandhi said "everybody" in the party and government was responsible for the defeat.

"How can you blame any individual for this result? It is the collective responsibility of both the party and the government. All, including myself, are responsible for the party's loss," Ahmed Patel told The Indian Express newspaper.

Senior Congress leader Ashwani Kumar has called for "transformative changes" in the party which would allow "honest dissent".

"She [Sonia Gandhi] must now take hard decisions to correct the aberrations that have debilitated the party, starting with transformative changes in the way we conduct our own politics and organisational affairs," he told the newspaper.

Party MP and former minister Kamal Nath has attributed the debacle to the party's "disconnect with ground realities".

Analysts like Milan Vaishnav, of the Carnegie Endowment for International Peace, say that though Congress is facing one of the toughest challenges in its history, it is premature to write the party's obituary.