Modi’s Bharatiya Janata Party (BJP) won 240 seats on its own, or 32 short of half the 543 members in parliament’s lower house, but formed the government, as his 15-party National Democratic Alliance (NDA) won 293 seats.
The opposition INDIA alliance led by Gandhi’s centrist Congress party won 230 seats. Congress on it own won 99.
The Election Commission did not respond to the comments.
In response, Agricultural Minister Shivraj Singh Chouhan said Gandhi was trying to besmirch the image of the nation, an activity he sought to portray as treasonous.
“Due to being defeated consecutively for the third time, anti-BJP … anti-Modi sentiments have taken root in his mind,” Chouhan told reporters.
“He is constantly trying to malign the image of the country, which is equivalent to treason.”
In the weeks before the vote, Gandhi’s Congress party received income tax notices, seeking payments of about 35 billion rupees (US$417 million), which it described at the time as politically motivated.
It was eventually given time to resolve the payments until after the vote.
The accusation that voting was not entirely free is not new, with Congress and some allies in the opposition alliance having aired accusations of voting machines having been tampered with in prior elections since Modi won power in 2014.
In public denials, the Election Commission has said its systems are secure and cannot be interfered with. India’s Supreme Court has also rejected petitions seeking a return to the old system of balloting.