US President Donald Trump has started dismantling a government programme which protects hundreds of thousands of young immigrants who were brought into the country illegally as children.

Attorney General Jeff Sessions declared the Obama administration’s programme “an unconstitutional exercise of authority” that must be revoked.

New applications will be halted for President Barack Obama’s Deferred Action for Childhood Arrivals (DACA) programme, which has provided nearly 800,000 young immigrants a reprieve from deportation and the ability to work legally in the US in the form of two-year, renewable work permits.

The administration is giving Congress six months to come up with a legislative fix – “should it choose to”, according to Mr Sessions – before the government stops renewing permits for people already covered by the programme.

According to Department of Homeland Security officials, people with permits whose renewals are set to expire between now and March 5, 2018 will be able to re-apply – so long as their applications are submitted by October 5 this year.

No permits will be revoked before their existing expiration dates and applications already in the pipeline will be processed, they said.

In a statement, Mr Trump said the change would be “a gradual process, not a sudden phase-out”.

He added: “In effect, I am not going to just cut DACA off but rather provide a window of opportunity for Congress to finally act.”

He said he did not favour punishing children for the actions of their parents but added “we must also recognise that we are a nation of opportunity because we are a nation of law” and “young Americans have dreams too”.

His action drew swift criticism from many immigration advocates and Democratic lawmakers.

(Carolyn Kaster/AP)
(Carolyn Kaster/AP)

House Democratic leader Nancy Pelosi called Mr Trump’s decision “a deeply shameful act of political cowardice and a despicable assault on innocent young people in communities across America”.

Some Republicans objected, too, with senator John McCain of Arizona saying Mr Trump was taking “the wrong approach”.

The announcement came the same day as a deadline set by a group of Republican state officials who said they would challenge DACA in court unless the Trump administration rescinded the programme.

Administration officials argued the programme might not hold up in court – and said that allowing the lawsuit to proceed would throw the programme into far more chaos than the move they chose.