The Trump administration has declined to renew the temporary protected status of Salvadoran immigrants to the US, giving an estimated 263,000 people less than two years to leave the country or be deported.

The Temporary Protected Status (TPS) designation has allowed immigrants from El Salvador to live and work in the US since 2001, when a pair of earthquakes crippled much of the Central American nation.

Immigrants will have until September 2019 to leave the country or find other means of lawful residency, according to multiple news reports.

In a letter to Congress members, Homeland Security secretary Kirstjen Nielsen said conditions in El Salvador had improved significantly since 2001, rendering the original justification for the protected status void.

Congress now has 18 months to pass legislation protecting Salvadoran immigrants or their legal status will be revoked, according to a letter first seen by The Washington Post.

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The US Department of Homeland Security (DHS) occasionally grants protected status to immigrants from countries where conditions “prevent the country’s nationals from returning safely”, or where the country is “unable to handle the return of its nationals adequately”. The designation must be renewed in six, 12 or 18-month periods.

Every president since George W Bush has extended the protected status of Salvadorans, allowing many to create permanent lives within the US. More than half of all Salvadoran immigrants have lived in the US for 20 years or more, according to the Centre for Migration Studies. 10 per cent are married to a legal resident.

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Amanda Baran, a consultant to the Immigrant Legal Resource Centre, called Monday’s decision “reckless and heartless”.

“El Salvador is one of the world’s most dangerous countries, and will be unable to absorb the return of these thousands of people whose lives are inextricably intertwined with those of ours here in the United States,” she said in a statement.

Amnesty International also decried the decision, claiming the US "could be sending people to their deaths".

More than 1,000 people died and thousands more lost their homes in the 2001 earthquake in El Salvador. While the country has since rebuilt, poverty and gang violence remain rampant.

El Salvador was ranked the third most dangerous nation on the globe by the World Economic Forum in 2017. The country’s homicide rate remains one of the highest in the world, with a reported 80.94 homicides per 100,000 inhabitants in 2016.

The Obama administration cited drought, poverty and widespread gang violence – among other things – as reasons for renewing the TPS in 2016.