"If you do not have democracy in your home (party) how can you practise it in the country," Modi asked.
"What is the result everybody knows," he said, prompting the crowd to reply that the post would go to (Congress vice-president) Rahul Gandhi.
Gandhi is likely to be elected Congress president in the ongoing organisational polls.
Modi went on to claim that this was a practice in the Congress party.
"Sardar Patel got more votes than Jawaharlal Nehru when the Congress party had (then) met to decide who would be the prime minister of the country. But that election was rigged and Nehru won," he alleged.
This is what happened with Morarji Desai, too, Modi said.
"They have a history of rigging elections," he charged.
Referring to Congressman Shehzad Poonawalla by his first name, Modi said he had raised questions over the process of elections and had alleged it was being rigged.
"They keep on muttering words like tolerance, tolerance, tolerance... But the party has brought out a diktat to silence this youth. The party has gagged him from all WhatsApp groups; he has been collectively boycotted by that party," the prime minister claimed.
"We have a Gujarati saying which means that a bucket can get filled only if there is water in the well. If you do not have democracy in your home (party) how can you practise it in the country," Modi said.
The prime minister is slated to address another election rally later in the day. Gujarat will vote in two phases to elect a 182-member Assembly on December 9 and 14.