The deaths of at least 23 Indian children poisoned after eating a free school meal has triggered an outcry over food safety just as the ruling Congress party is set to launch an ambitious plan to feed 800mn poor, with an eye on elections due within a year.

Congress leader Sonia Gandhi’s national subsidised food project includes free school meals and expands existing handouts to make it probably the biggest welfare initiative since India gained independence in 1947.

The National Food Security Ordinance aims to give 5 kg (11lb) of cheap grain every month to 800mn people and more than doubles the reach of the existing subsidised food system, whose failings still mean the country is home to a quarter of the world’s hungry.

But the school tragedy in Bihar state, the nation’s second poorest, highlights the potential dangers of rolling out a major food distribution scheme without strict monitoring of supplies and quality and having to hand responsibility to local authorities, many of whom have weak administration.

Currently, nearly half of India’s annual rice and wheat supplies are lost to rot or corruption, and while deaths from contaminated food are rare, many of the country’s poor are offered substandard food, sometimes containing stones and grit.

“This (tragedy) does throw light on food quality in public programmes,” said Dipa Sinha, Right to Food researcher and activist. “It is clearly a failure of monitoring and accountability.”

Under Gandhi’s food welfare plan, grain distribution will be devolved to local communities, but critics say few details have been revealed and question how the scheme will be administered. The Bihar tragedy may raise more questions over Gandhi’s plan.

The Congress party, which controls only half of India’s 28 states, won the last two elections after introducing populist policies such as a rural jobs plan and a $12.5bn farmer loan waiver.

The food security bill, Gandhi’s pet project, was approved on July 3 using executive orders, usually reserved for urgent policy. Gandhi plans to launch the programme on August 20, the birthday of her late husband and former prime minister, Rajiv.

Parliament must decide whether to agree or reject the measures within six weeks of the next session’s start on Aug 5. While opposition parties and some government allies complained about the decision to use an executive order to drive the plan through, the bill is expected to be approved.

Under the scheme India, one of the world’s largest food producers and consumers, will buy about 30% of its 198mn tonnes of rice and wheat output to sell at subsidised prices. The scheme will cost an estimated $22bn a year.

Bihar’s chief minister Kumar, not a Congress party member, has succeeded in reviving the state’s economy since coming to power in 2005, but has struggled to feed the millions of poor due to continuing corruption and a lack of storage.

Kumar is slowly making progress and, in a warning for Gandhi, it is the chief minister and not Congress that is winning praise among farmers and beneficiaries for the efforts.