India's opposition Congress party suffered a major blow yesterday when parliament disqualified its leader, Rahul Gandhi, a day after a court convicted him of defamation for comments that many deemed insulting to Prime Minister Narendra Modi.

Gandhi "stands disqualified from the membership of Lok Sabha from the date of his conviction", the lower house of parliament said in a notice, using its Indian name.

Gandhi, 52, was convicted and sentenced to prison for two years in the western state of Gujarat on Thursday after he was found guilty of defamation in connection with a 2019 speech in which he referred to thieves as having the surname Modi.

He is due to appeal against the verdict in a district court in Gujarat, also Modi's home state.

"I am fighting for the voice of India, I am ready to pay any cost," Gandhi tweeted hours after his disqualification.

Gandhi made the thieves comment while campaigning ahead of the last general election in which Modi and his ruling Hindu-nationalist Bharatiya Janata Party (BJP) swept back to power.

The court case was filed by BJP member Purnesh Modi, who focused on a comment Gandhi made in the 2019 speech when referring to two fugitive businessmen, both surnamed Modi.