President Pranab Mukherjee signed the Ordinance that will give the nation's three-fourth population the right to get 5 kg of foodgrains every month at highly subsidised rates of Rs 1-3 per kg.
The President's assent came two days after the Cabinet gave its approval to the landmark programme pushed by UPA Chairperson Sonia Gandhi, brushing aside political opposition from allies and others.
The Food Security programme will be the biggest in the world with the government spending estimated at Rs 125,000 crore annually on supply of about 62 million tonnes of rice, wheat and coarse cereals to 67 per cent of the population.
The Ordinance comes before the Monsoon session of Parliament which usually begins towards the end of July or early August.
Political parties, including UPA's outside ally Samajwadi Party, have slammed the government's rush to come out with the Ordinance saying such a measure should have been properly debated in Parliament before being enacted.
Rejecting allegations that the measure was hurried up with an eye on elections, Congress said it will be a "game changer" that will provide right to cheap food grains to 82 crore people.