Millions of poor people could lose access to vital food stamps under proposed rule changes by the Trump administration.

New rules proposed by the Department of Agriculture (USDA) would see stricter work requirements for food stamp eligibility, and change the way 40 states enrol families into the programme, officially called Supplemental Nutrition Assistance Program (SNAP).

Approximately 20 million households with 40 million individuals used the SNAP program in in 2018, which gives people a monthly supplement to buy nutritious food in the form of a special debit card.

Now an in-depth study on the rules’ likely effects - by the Urban Institute - concluded that 3.7 million fewer people would receive SNAP in a typical month, 2.2 million households would see their average monthly benefits drop by $127, and almost a million students would lose access to free or reduced lunches.

Some states would be particularly badly hit. Nevada, for instance, could see up to 22 per cent of recipients lose access to food stamps.

In seven states, however, the changes would give more people food stamp access. These include Missouri, Tennessee, Utah and Virginia.

Craig Gundersen, an agricultural and consumer economics professor at the University of Illinois at Urbana-Champaign who has studied the program for more than two decades, said 50 per cent of the 3.7 million SNAP beneficiaries were already food insecure.

"The essential goal of the program is to mitigate hunger and its consequences in the United States,” he told NBC News.

"Anything that impedes SNAP of doing that is very problematic as it leads to food insecurity in our country."

The USDA believes the changes will reduce the SNAP budget by about $4.2bn.

In a USA Today column, secretary of agriculture Sonny Perdue said: “At USDA, our informal motto is ‘Do Right and Feed Everyone’. With these proposed improvements, we will ‘do right’ by the taxpayers and restore the dignity of work to the able-bodied who receive SNAP benefits.