Although the full impact of the pandemic cannot yet be determined, the report estimated around 118 million more people faced hunger in 2020 than in 2019, an increase of 18 per cent.
The rise in moderate or severe food insecurity was equal to the previous five years combined.
"Nearly one in three people in the world (2.37 billion) did not have access to adequate food in 2020–an increase of almost 320 million people in just one year," the report said.
One in 10 people were undernourished.
The increase in hunger was widespread as the economic downturn affected almost all low-and-middle-income countries.
But the biggest impact was in countries where there were also climate-related disasters or conflict, or both.
"The Covid-19 pandemic is just the tip of the iceberg," said the report.
"More alarmingly, the pandemic has exposed the vulnerabilities forming in our food systems over recent years as a result of major drivers such as conflict, climate variability and extremes, and economic slowdowns and downturns."
The UN agencies said there is a unique opportunity to reverse the dynamic this year however, thanks to two major food and nutrition summits plus the COP26 meeting on climate change.
The report was jointly published by the Food and Agriculture Organization of the United Nations, the International Fund for Agricultural Development, the United Nations Children's Emergency Fund, the UN World Food Programme and the World Health Organization.