Western Europe's poorest country is likely to lose 40% of the €20 million in food aid it gets from Brussels every year, according to Isabel Jonet, who heads the Food Banks charity.
Her institution supports 390,000 poor people out of Portugal's 10.5 million population. They have been helped by the EU's "Food for the Needy" program which is due to be replaced by the Fund for European Aid.
The new fund will have fewer resources for food, Jonet said. And the cash-strapped government has made no preparations to deal with the problem, she added.
"Unlike in other countries, Portugal does not yet have a plan to make up for the changes or for a delay in the new scheme coming through, so there may be an interruption in our distribution of food," Jonet said.
The number of those in need in Portugal has risen, as unemployment has hit record highs this year.
The economy has struggled through its worst recession in decades due to austerity measures imposed under an €8 billion EU and International Monetary Fund bailout.
"Unfortunately more and more people need this help by the day. Although small, it makes a huge difference," said a tearful Maria Mendes, 50, picking up food staples at a charity that caters for 300 people in Lisbon's old neighborhood of Graca.
Official data released in July showed that last year, 22% of the Portuguese were suffering from material deprivation, including almost 9% from severe deprivation.
The minimum wage in Portugal is €566 a month, compared with neighboring Spain's €753.
People are considered materially deprived when their income is not enough to meet basic needs like having a meal of fish or meat every other day, pay for rent, or warm their homes.
The government says it is looking at the food aid issue but gave no concrete promises to answer Jonet's concerns.
"We are working to ensure that the funds are enough to keep such a fundamental project going," Social Affairs Minister Pedro Mota Soares said. "Let's finish the negotiation process in Europe and then we'll see where we stand."
Although the current Food for the Needy scheme ends this year, there is no set deadline for the European Parliament and European Council to agree on the aid fund which will replace it.
At stake is about a third of the 44 tonnes of food that Portugal's Food Bank distributes through a network of charities and public partners every day. The rest comes from the food industry and citizens' donations.
Asked to comment on Jonet's concerns, Jonathan Todd, a European Commission spokesman for employment and social affairs, said he could not provide a country breakdown as the new fund's regulations were still being discussed.
He confirmed that the current program would end this year, and the Fund for European Aid to the Most Deprived that will replace it envisages co-financing by member states.
But overall, the new fund should increase the resources available to make assistance broader than just food, he said.
Cry for help
Meeting deficit targets and reining in public debt may be the main concerns of lenders trying to get Portugal's economy back on its feet, but for many Portuguese the economic cure has been painful.
"Requests for help are piling up. We have many new unemployed and members of middle-class families who lost their jobs and now need help," said Susana Ambrosio, director of the Maria Roque Pereira Foundation, a Food Bank partner where Mendes gets her food basket.
Mendes, who had to quit her supermarket job after being diagnosed with cancer, has a husband who is unemployed and two children studying, had a message for the EU food policy makers.
"Please think about those who struggle, many of them are not speaking up because they are ashamed. Please consider all the other bad things the government is already doing to us," she said.