Francesco Rocca, President of the International Federation of the Red Cross, said the organisation's emergency appeal in September for some 50 million Swiss francs ($50.1 million, 45.5 million euros) for aid to Venezuela was less than 10-percent funded.
"This is not about resources, this is about political will," he said, warning that the severe underfunding meant vital medical treatments, medicines and food could not be provided.
United Nations agencies and other humanitarian actors were facing the same lack of funds for Venezuela operations, and as a result, many people in the country were "starving and dying", Rocca said.
He warned that there were some who wanted "to use the civilian population, their desperation, as a tool to destabilise the country".
Venezuelan President Nicolas Maduro remains in power through the support of his security forces, while more than 50 countries, including the US and Brazil, have recognised opposition leader Juan Guaido as the nation's acting leader.
More than 4.5 million people have meanwhile left the country, which is in the midst of its worst economic and social crisis in recent history, suffering from severe shortages of power and resources, as well as crippling US sanctions.
Many of those remaining in the country are "in desperate need," Rocca said, denouncing international donors' unwillingness to help.
He pointed out that funding appeals for humanitarian aid in other crisis situations were not facing the same problems.
After a hurricane hit the Bahamas in September for instance, the organisation's appeal for 12 million Swiss francs was met and surpassed by eight million francs within 10 days, he said.
Even drawn-out conflicts where humanitarians have long warned of donor fatigue are proving easier to raise funds for than Venezuela, according to the IFRC.
"The paradox is that for us it is easier to receive funds for Syria and even for Yemen," Rocca said.
"I cannot think of anything else than political will to create this kind of situation on the ground," he said.
"As a humanitarian this is unacceptable."
"Helping people in Venezuela is not... a political act. It is the only way to alleviate their suffering," Rocca said.
He dismissed the "legend" that the humanitarian crisis was still being exacerbated by the government blocking access to aid, insisting that the Red Cross was able to "deliver everything in a very free" way.
"But unfortunately now we are stuck", he said, lamenting that there was little left to deliver.
"The needs are not met at all," he warned.