Gandhi’s former adviser Sam Pitroda accused Mr Modi of using tactics borrowed from the US President, using immigrants as a scare tactic. Mr Modi is currently trying to get re-elected in what is the world’s largest political elections. But this latest blow comes as his popularity has nosedived among Indians, with many now said to support his rival Rahul Gandhi.
Mr Modi leads the Bharatiya Janata Party while Mr Gandhi in charge of Indian National Congress.
Mr Pitroda has been a vocal critic of the way in which Mr Modi has handled his campaign, especially his use of immigration.
He said: “The strategy was, there is an enemy at the border, in that case, it was Mexican, and enemy, also, as people in the country, immigrants.
“Very similar, Modi says there is an enemy at the border. Anything you say, immediately everyone attacks you.”
Polls predict Mr Modi should just squeeze out the majority he needs to continue ruling the country.
Five years ago he had vowed to turn India into an economic and military power.
But half-a-decade later and the country is unable to create a million jobs every month or ease farmers’ distress over low prices for their products.
The Congress Party is also catching up because of a feeling of unrest in countryside areas over a weak rural economy and lack of jobs for young people.
Recent tensions with Pakistan have ramped up the pressure on Mr Modi.
India carried out air strikes in February on a suspected militant camp based in Balakot, Pakistan, who had claimed responsibility for a deadly car bombing in Kashmir.
Pakistan responded by sending warplanes into Indian Kashmir the next day.
Around 900 million people are eligible to vote in the elections, which will begin on Thursday.