"This cholera scandal is entirely man-made by the conflicting parties and those beyond Yemen's borders who are leading, supplying, fighting and perpetuating the fear and fighting," Stephen O'Brien told the UN Security Council.
The humanitarian crisis "is a direct result of the conflict and serious violations of international law," he said.
More than 320,000 suspected cholera cases have been reported in nearly all of Yemen's districts and at least 1,740 people have died from the outbreak, said O'Brien, the UN under-secretary-general for humanitarian affairs.
Describing the humanitarian crisis as "appalling", Yemen's UN envoy Ismail Ould Cheikh Ahmed said the country was in the throes of not "a single emergency but a number of complex emergencies".
More than seven million people are at risk of famine including 2.3 malnourished children under the age of five in Yemen, already among the Arab world's poorest countries.
Yemen's health system has collapsed during the war pitting the Saudi-led coalition backing the internationally recognized Yemeni government and Iran-backed Shiite Huthi rebels since March 2015.
The Huthi rebels still hold the capital Sanaa and Taez, the country's third largest city.
O'Brien appealed for $250 million in funding for the UN response to the cholera crisis. So far, only $47 million has been received.
He also urged council powers to take action to ensure public servants are paid so that health facilities can reopen.
The airport in Sanaa, which closed last year, must be reopened and the port of Hodeida, a crucial lifeline for deliveries of food and medicine, must be kept safe from attack, O'Brien said.
The aid chief urged Saudi Arabia to allow mobile cranes left in Dubai to arrive at Hodeida port.
Riyadh has accused the Huthi rebels of using the port to smuggle weapons into the country.
"You will have to lean much more heavily and effectively on the parties and those outside Yemen who are leading this policy and action," O'Brien told the council.
