Donald Trump’s “blatantly unconstitutional” order to end birthright citizenship has been blocked by a federal judge, representing the first major roadblock to his policy agenda.

A federal judge in Seattle on Thursday blocked Mr Trump’s executive order, issued earlier this week, which would have ended the right for people born in the US to claim American citizenship.

Birthright citizenship was established in 1868 and is enshrined in the 14th Amendment of the US constitution. It allows anyone who is born on US soil to become a citizen, even if their mother entered the country illegally.

Mr Trump has said the rule has resulted in birth tourism and given rise to “anchor babies”, which are used by undocumented migrant parents to claim the right to live in the US.

His order to end the practice has been challenged by 22 states in five separate lawsuits.

The first of the cases, brought by Arizona, Illinois, Oregon and Washington, was heard on Thursday.