Gandhi "stands disqualified from the membership of Lok Sabha" — the lower house of India's parliament, a statement said.
Indian lawmakers took the action against the leader of the Congress party as his supporters gathered in some parts of the country to protest his conviction and sentencing to two years in prison.
The 52-year-old was found guilty of defamation over a speech he gave in 2019 in which he referred to people with the surname Modi — such as current Prime Minister Narendra Modi — as thieves.
Members of the Congress party have said that the sentencing of Gandhi — a descendent of the powerful Nehru-Gandhi family — was politically motivated, pointing to Modi's ruling Bharatiya Janata Party (BJP).
Setback for opposition party
News site India Today reported that Gandhi will now not be able to contest elections for eight years, a major setback for the opposition party.
"I'm stunned by this action and by its rapidity, within 24 hours of the court verdict and while an appeal was known to be in process," Shashi Tharoor, a Congress lawmaker in parliament, said.
"This is politics with the gloves off and it bodes ill for our democracy."
Gandhi was set to face Modi at the ballot box next year, an election in which Modi will be seeking his third term in office.
Although Congress dominated Indian politics in post-independence India, their number of elected seats in the lower house has fallen to less than 10%, having been thwarted by the BJP in the last two elections.
Even before the disqualification of the main opposition party, Modi was expected to win the upcoming general election and remains India's most popular politician.
ab/rc (Reuters, AFP)