"We have roughly 40 percent of the population that are in need of humanitarian assistance," Mishra told AFP. "10.3 million people in this country need help."
The isolated North industrialised rapidly following the end of the Korean War and for a time was wealthier than the South. But funding from Moscow came to an end with the collapse of the Soviet Union, which was followed by a crippling famine and chronic economic mismanagement.
Under current leader Kim Jong Un it has made rapid progress in its nuclear and ballistic missile programmes, earning itself multiple sets of UN Security Council sanctions, with more measures imposed unilaterally by the US, EU, South Korea and others.
The impoverished North has been frequently condemned by the international community for decades of prioritising the military and its nuclear weapons programme over adequately providing for its people -- an imbalance some critics say the UN's aid programme encourages.
The latest sanctions remain in place despite a rapid diplomatic rapprochement on the peninsula, with a North-South summit due later this month ahead of talks between Kim and US President Donald Trump.
Kim has also quietly introduced some market reforms under a policy of simultaneously developing the economy and the military, with its estimated growth rate rising -- the North itself does not publish the statistic -- but it remains deeply poverty-stricken.
"Undernutrition continues to be a serious concern with more than one quarter of the children stunted due to inadequate nutritious food, people struggling to have basic access to facilities including health, a large proportion of the population lives without a reliable source of safe drinking water, almost a quarter without basic sanitary facilities," Mishra said.
The UN sought $114 million from donors last year for food security, nutrition, health, and water and hygiene, but received only $31 million.
Out of 4.3 million people it targeted for food assistance, only 660,000 received help -– just over 15 percent.
"We did not have the funding to support all the need, so we were only able to provide this," Mishra said, adding he had not previously seen a similar statistic during his career.
A higher proportion, two million out of a targeted 2.5 million, received nutritional support, which is cheaper to provide.
But he urged donors to delink geopolitical considerations from humanitarian decision-making, saying that "even in war", humanitarian principles have always sought to prioritise those in need.
"Humanitarian considerations should be separate," he said, "regardless of all the geopolitical issues".
The UN this week launched its "Needs and Priorities" assessment for North Korea this year, seeking $111 million in funding.
In the foreword to the document, Mishra, who is Indian, wrote: "The geopolitical environment has meant that the situation for many people in the country has been largely forgotten by the rest of the world."
The sanctions imposed on the North were not intended to affect civilians or restrict humanitarian activities, he added, but in practice aid supplies and payments were "often significantly delayed and disrupted, notably due to the perception of risk of violating the sanctions by banks, suppliers and officials".
Even hand-driven tractors provided by the UN's Food and Agriculture Organization had been held up at the border, he told AFP.
Experts say that North Korea needs to produce around 6.5-6.7 million tonnes of food to feed its population, but usually grows around one million tonnes less than that, leading to chronic shortfalls.
Aid agencies used to class all those who relied on the country's Public Distribution System –- 18 million people –- as facing food insecurity.
The state-controlled ration usually provides far less than its goal of 573 grammes of food a day. But North Koreans also have access to other sources of food, such as private markets and land plots.
Under the international standards of the FAO's State of Food Security and Nutrition in the World report, 10.3 million North Koreans are now considered to be undernourished.
The North faces geographical challenges –- less than 20 percent of its land is suitable for agriculture, with most of the rest made up of mountains and forest, and it is sometimes hit by droughts and floods.
But its agriculture is officially still run on a co-operative farm system and crop yields are relatively low.
It has benefited from few of the global advances in agricultural technology, fertilisers and seeds of recent decades. Such assistance would be considered development aid rather than humanitarian, and so is not possible under sanctions.