Threatened cuts to US nutrition programmes will offset all voluntary food donations to the poor this year, according to the authors of a major new report on hunger, who say it is time for charities and church groups to devote more time to political campaigning.

According to a recent government survey, in 2012, due to poverty, an estimated seven million American households struggled to provide enough food. Despite this, a joint committee of Congress is currently meeting to consider welfare cuts of $40bn. An existing $11bn worth of cuts to the food stamps system, known as Supplemental Nutrition Assistance Program (Snap), began to take effect on 1 November.

On Monday the Bread for the World Institute, a Washington policy group backed by religious charities, published a report entitled Ending Hunger in America. The report proposes a number of responses to the problem, such as measures to promote full employment. The researchers claim that the flurry of voluntary food bank activity which tends to happen around Thanksgiving will be dwarfed by the political impact of cuts, if legislation passed by the House of Representatives is adopted.

“Virtually every church, synagogue and mosque in the country is now gathering up food and distributing, and all of that work that food banks do comes to 5% of the food that needy people get,” said the Bread for the World president, Reverend David Beckmann. “95% comes from school breakfasts, lunches, food stamps and WIC, so Congress can say 'We can cut this programme 5% per cent – no big deal.' But if you cut the national nutrition programmes 5%, you cancel out everything that the charitable system is doing.”

Religious charities argue that the unprecedented threat to public safety nets necessitates a much more aggressive political response from the voluntary sector, which has traditionally focused on grass-roots community work.

“We have got to flood Congress with protests about the cuts in Snap,” said Reverend Beckmann, who said such cuts would “deepen hunger for six million Americans”.

John Carr, director of the Initiative on Catholic Social Thought and Public Life at Georgetown University, pointed out that crunch meetings on Capitol Hill would co-coincide with an international day of fasting, proposed by Pope Francis as a protest over world hunger, on 10 December.

“We call it by lots of names like 'food insecurity', the reality is it's an empty cupboard at the end of the month, it's a mum who misses a meal so she can feed her kids,” he said. “But while we are talking about Thanksgiving and hunger, up on the Hill, the conference committee on agriculture is figuring out whether to cut food stamps by $40bn or $4bn a year. That's not the kind of national Thanksgiving conversation we ought to be having.”

Carr agreed that increased political activism was needed, but said it should not take away from donations. “I am part of the faith community and I am so proud of what we do every day to feed hungry people,” he said. “But we know that while we do what we can, it does not substitute for just and compassionate policies, so we need to organise, help hungry people have a voice. “

At a launch event for the report, Sharon Thornberry, a food bank manager from Oregon, described efforts to move into political organising and spoke of the downside of reliance on voluntary donations. “I have been on both sides of the counter in community food programmes and when you stand in line getting an emergency food box it takes something away from you,” she said.

“There are people who believe that you are undeserving in some way so it's OK to cost you emotionally to get that food box but despite the fact that we have a massive system that provides food in the country, we don't feed people's souls with that.”

Barbie Izquierdo, another anti-hunger activist, spoke of having to tell her children to skip lunch so dinner could be put on the table.

“My children started school in Philadelphia this year and they had to sign an anti-bullying pledge,” she said. “When I go to Congress I feel like they should sign an anti-bullying pledge.”