International concern for the lives of tens of millions of Yemenis is rising amid fears of a military attack on Hodeida, a vital Red Sea port that is the main entry point for aid and imports.
The Norwegian Refugee Council (NRC), a non-governmental organisation, said commercial food imports were at an "all-time low, driving the price of basic commodities to rise on average by a third".
"This makes Yemen the largest food security crisis in the world," said NRC secretary general Jan Egeland at a press conference in the capital Sanaa.
"Nowhere on earth are as many lives at risk," he said.
"This is a gigantic failure of international diplomacy."
Signup to our newsletter and follow us on Facebook and Twitter!
The NRC chief appealed to "men with guns and power" in Yemen and around the world to broker a ceasefire and return to the negotiating table to find a solution to the war.
A Saudi-led military coalition for two years has fought Shiite Huthi rebels allied with Iran for control of Yemen.
More than 7,700 people have since been killed and around three million displaced, according to the United Nations.
The Huthis control a string of strategic ports on the Red Sea coastline along with Sanaa and much of the northern highlands.
Rights groups fear the Saudi-led coalition is planning to attack Hodeida, which would likely destroy the port and cut supplies to millions of hungry civilians.
A spokesman for the coalition has denied the alliance plans to launch an offensive on Hodeida.
The United Nations warns 17 million Yemenis -- 62 percent of the population -- are unable to access food.
A third of the country's provinces are on the brink of famine.