NEW DELHI -- The "final assault" on poverty has begun, declared Rahul Gandhi, the leader of India's main opposition party the Indian National Congress.

Gandhi this week promised to hand out a total of 3.6 trillion rupees ($52 billion) annually to tens of millions of the vast nation's poorest people, in a bold bid to claw back ground on Prime Minister Narendra Modi ahead of general elections in the world's biggest democracy.

The gap in public support between Gandhi and Modi has widened after the incumbent ordered airstrikes on alleged terrorist targets in Pakistan last month. This appears to have prompted the challenger to go all-out in a last-minute attempt to woo voters in the seven-phase elections that will run from Apr. 11 to May 19.

On March 25, Gandhi said his Congress party would guarantee each of the 50 million poorest families an annual payment by bank transfer of 72,000 rupees. That money, he said, would help 250 million people -- about 20% of the country's population.

He said the scheme -- called "Nyay" (justice) -- was the biggest of its kind in the world.

"Entire calculations have been done. Fiscal repercussions of this have been analyzed. This money is perfectly available. This scheme is perfectly doable. We are going to deliver this scheme," he said, adding that the party would soon provide further details.

But Modi's Finance Minister Arun Jaitley blasted the announcement as a "bluff."

Jaitley said Gandhi's grandmother and former Prime Minister Indira Gandhi came up with the legendary slogan of "garibi hatao" (remove poverty) in 1971, but she "just redistributed poverty."

"For two-thirds of the last 48 years her party has been in power. Yet, they left behind a legacy of poverty," he said.

While Gandhi's plan is estimated to cost 3.6 trillion a year, Jaitley said the Modi government was already spending 5.34 trillion rupees to help the country's poor and farmers in the form of food, fertilizer, health care subsidies and income support.

Economist Surjit Bhalla, a former member of Modi's economic advisory council, wrote on Twitter: "Is [Gandhi's scheme] a game changer or absurd beyond compare? The idea is fundamentally flawed and so beyond compare."

Rajiv Kumar, vice chairman of the government policy think tank Niti Aayog, said the scheme equated to 2% of gross domestic product and 13% of the government's budget and would "ensure that real needs of people remain unsatisfied."

"True to its past record of promising the moon to win elections, [the] Congress President announces a scheme that will [bust] fiscal discipline, create strong incentives against work and which will never be implemented," he tweeted.

Modi had been taking flak over rising unemployment and agrarian distress, but nationalist sentiment appears now to be overshadowing the economy and other critical issues -- especially since the airstrikes.

Support for Indian Prime Minister Narendra Modi has soared since he ordered airstrikes against alleged terrorist targets in Pakistan last month. © Reuters

Gandhi's approval ratings, in contrast, have dropped sharply over the past month or so. His scheme does, however, have its supporters.

Prashant Bhushan, a public interest lawyer in the Supreme Court of India, tweeted that Gandhi "seems to have stolen the narrative from [the Baharatiya Janata Party] by his minimum income guarantee scheme. If implemented properly this could be more revolutionary than [a rural employment program] which was a game changer for 2009," he said, referring to the elections for Congress that year.

"A small tax on wealth, inheritance and business turnover can pay for this," he said.

Sunil Kumar Sinha, principal economist at India Ratings & Research, a Fitch Group company, said that without details it was too early to assess the fiscal viability of the scheme.

"What we have at the moment is the top-line figure and using that to arrive at various conclusions may be wrong," he told the Nikkei Asian Review. "[It is not known] how the scheme will be rolled out, whether it will subsume existing subsidies or whether it will be a top-up scheme."

He added that it was not uncommon for a party to make such announcements "to catch the attention of voters."

On Tuesday, Congress spokesperson Randeep Singh Surjewala told reporters that the income scheme would be women-centric and would include the poor in both urban and rural areas.

The money would go into the bank account of the woman of the family, he added.