Donald Trump proposed designating all migrants entering the US without permission as “enemy combatants” and shipping them to Guantánamo Bay to be detained alongside hardened terrorism suspects, according to a new book written by an anonymous author described as “a senior official in the Trump administration”.

Among the many incendiary details contained in A Warning, a behind-the-scenes account of the White House under Trump, is the revelation that the president floated the idea of changing the legal designation of migrants as a way of forcibly keeping them out of the country. The change would effectively have condemned all undocumented migrants to the same legal treatment as the al-Qaida architects of 9/11.