Congress sources say that the party could promise an income of Rs 1,500 to Rs 1,800 for individuals under a certain economic level.

The government's 2016 Economic Survey, signed-off by the then Chief Economic Adviser Arvind Subramanian, had pitched a plan for a universal basic income of around Rs 630 per month.

The idea of universal basic income is gaining traction in wealthier countries such as Finland and France. India has had rapid economic growth but is still home to one in three of the world's extreme poor, with millions more at risk of becoming poor from an emergency medical payment or bad harvest.

Congress officials have told news agency Reuters that funds for the scheme will be channeled from those spent on food subsidies and other programmes.

BJP spokesperson Gopal Krishna Agarwal said the promise was untenable. "Where will the money come from? He's promising the moon to fool the people," he was quoted by the agency as saying.

Mr Agarwal added that the current government had dabbled with the idea in 2014. They came to the conclusion that even if all the subsidies are done away with, there would be enough funds to pay Rs 6,000 per family per month, which is not enough.

Luke Martinelli, research associate at the Institute for Policy Research, University of Bath said the Congress move was significant, although short of universal coverage.

"Obviously, a means tested guaranteed income for the poorest is very different from a universal basic income per se. Having said that, obviously, in terms of income security there are some significant overlaps and this will be treated with enthusiasm, I'm sure, by the basic income community," he said.

India's 2018/19 food subsidy bill alone was estimated at 1.7 trillion rupees, roughly 7 percent of total federal spending.