The latest monthly nutritional survey in the capital, Conakry, showed that moderate acute malnutrition rose to 8.4 percent in December from 6.9 percent in November.
Families are increasingly bringing children to NGO-supported nutritional centres but because of a shortage of corn-soya blend (CSB), vegetable oil and sugar - used for treating moderate acute malnutrition - WFP can no longer supply the centres as needed, according to agency officials.
"The demand for CSB is greater than the supply and currently we do not have the funds to furnish all nutritional centres," Foday Turay, WFP-Guinea head of programme unit, told IRIN.
"WFP is therefore appealing urgently for funds to replenish its stocks of CSB, as well as vegetable oil and sugar, so that we can continue providing much-needed nutritional support throughout Guinea."
WFP is seeking funds to help 25,000 children and 7,000 pregnant and lactating women.
Mamady Daffe, head of the Health Ministry's nutrition unit, told IRIN: "Resources for malnutrition treatment are quite limited and this means the situation is worsening by the day."
High child malnutrition rates are common throughout West Africa; some 4.5 million under-five children, or 9.9 percent, suffer acute malnutrition, according to the Food Security and Nutrition Working Group.
The World Health Organization's "critical" threshold for global acute malnutrition - comprising severe and moderate - is 15 percent.
WFP has long supported supplementary feeding for malnourished children, pregnant women and lactating mothers in Conakry and other cities throughout Guinea. With the socio-economic crisis after unrest in early 2007, WFP expanded the programme budget - calling for more supplementary foods - but funds have not come forward, agency officials said.
The latest political crisis in Guinea has exacerbated already dire living conditions. Chronic malnutrition has increased by 50 percent in the past five years, according to the UN Office for the Coordination of Humanitarian Affairs. An estimated 2.4 of Guinea's 9.8 million people are moderately or severely food insecure.
"A lack of understanding of nutritional needs is surely one factor contributing to malnutrition, but currently the main cause is economic hardship," the Health Ministry's Daffe told IRIN. "When people have almost nothing, they have a terribly difficult time feeding their families."
Sheryl Martin, head of Helen Keller International in Guinea, said a lack of supplies in local health centres was taking its toll on the population, and long-term solutions were needed. Due to the current rupture many centres must refer children to Conakry's main hospital, Donka.
"Health centres in [the neighbourhoods of] Dixinn and Kaloum must refer some children across town," she told IRIN. "When you can treat moderate malnutrition closer to where people live, you have a higher success rate because it is less costly for the family in terms of transport and other expenses."
She added that the closer a nutrition centre is to a family the more frequently the child can come - so his or her overall health can be monitored.
Martin said even if the current shortage is resolved, aid agencies and government health officials must put measures in place to avoid the impact of such crises in future.
"If health centres are low on supplies [for treating moderate malnutrition] we must have a system for moving supplies from other locations or substituting another product like Plumpy'nut [ready-to-use therapeutic nut paste]."
NGOs and Health Ministry officials are discussing options, including a pilot project to use Plumpy'nut for moderately malnourished children in urban settings; currently it is used for acutely malnourished children without medical complications, according to Martin.