While Rahul Gandhi initially said the "minimum income line" is Rs 12,000 per annum and the scheme will benefit individuals earning less than that, the Congress chief clarified that the scheme will supplement the income of the poor if it is less than Rs 12,000 per month.

"The minimum income line is Rs 12,000 per month. Whatever the difference - say the income is Rs 6,000 - we will top it up. Those who earn less than Rs 12,000, we will take their earnings to Rs 12,000," Rahul Gandhi said.

"It's an extremely powerful, extremely dynamic, extremely well-thought-through idea... We've done all the calculations, we've asked the best economists. They all backed us on this idea. We are going to implement it," Rahul Gandhi said, calling the programme a fiscally prudent scheme to be rolled out in phases.

The programme is likely to have a major impact on the country's exchequer, costing a huge Rs 3.6 lakh crore per annum, according to economists.

The proposed cash handout is seen as modelled loosely on universal basic income, a concept attracting growing interest around the world. Supported by Facebook founder Mark Zuckerberg among others as a way to reduce inequality, UBI involves people being given a flat lump sum by the state instead of subsidies and social security payments.

It has been tried out in several countries including Finland and Kenya, and has been promised by Italy's new populist government. In India, Sikkim's ruling Sikkim Democratic Front (SDF) has also promised UBI by 2022 as part of its 2019 assembly poll manifesto.

UBI had also been flagged in the 2017 Economic Survey as "a conceptually appealing idea" and a possible alternative to social welfare programmes targeted at reducing poverty.

The BJP dismissed the plan as an enticement on which Congress cannot deliver. Finance Minister Arun Jaitley called it a "bluff announcement" and yet another Congress bid to "cheat" the poor.

BJP also said the number of Indians below the poverty line had fallen to about 6.5 crore, or 5 per cent of the population, from 22 per cent in 2011. It reminded people of the direct cash support of Rs 6,000 a year for 12 crore poor farmers and cut taxes for the middle class last month.