Its study on the correlation between prolonged droughts in El Salvador, Guatemala, and Honduras and the increase in irregular migration to the US came amid renewed controversy over President Donald Trump’s intention to build a wall along the US-Mexico border to keep out illegal entrants.

He told a rally in Phoenix, Arizona, this week: “Believe me, if we have to close down our government, we’re building that wall.”

The WFP said its report showed the need to invest in long-term programmes to discourage people in the ‘dry corridor' from emigrating.

Some 47% of families interviewed for the report had insecure access to food, which the WFP said was a level “not been previously recorded in the region”.

Some 72% of families said they were applying emergency measures such as selling their land, farm animals and tools to buy food.

WFP regional director for Latin America and the Caribbean Miguel Barreto said: “The study provides an important insight into why people flee and the impact on the family members staying behind.

“It is perhaps this second aspect which makes this study stand out from much of the analysis conducted on migration from El Salvador, Guatemala, and Honduras to date.”

Family members left behind face the burden of paying the debts of those who have migrated. Relations of migrants to the US received a monthly remittance in 78% of cases and 42% of families said these were their only income.

More than half of the money received was to buy food.