India's main opposition Congress Party called a meeting of its highest decision-making body on Monday, following a letter from almost two dozen top leaders seeking changes to the way the party is run.

Long a dominant force in Indian politics, the Congress has suffered two heavy defeats in general elections by the Hindu-nationalist Bharatiya Janata Party, led by current Prime Minster Narendra Modi.

The letter, which calls for better decision-making within the party, is a rare challenge to the Nehru-Gandhi dynasty, which has dominated the Congress since India won independence from colonial power Great Britain in 1947.

The signatories of the letter expect the Gandhi family to either play a proactive role or step down, according to two sources in the party. Over 300 regional Congress politicians have supported the letter, they added.

Local media reported the party's interim president, Sonia Gandhi, would offer to resign, though several figures in the party, including the chief ministers of Congress-led states, have publicly backed her to continue.

“News of 23 senior most Congress leaders writing (a) letter ... is unbelievable and if it is true  it’s very unfortunate,” Rajasthan chief minister Ashok Gehlot tweeted, calling for Sonia Gandhi to stay on.

Supporters of the Gandhi family stood outside party headquarters in the capital New Delhi on Monday, holding placards and shouting slogans.

A meeting of the Congress Working Committee was scheduled to begin at 3pm.

Sonia Gandhi took over de facto leadership of the party last year from her son Rahul. His father, grandmother and great-grandfather have all served as prime minsters of India. — Reuters