Gun-toting US border guards with the power to search holidaymakers will be stationed at British airports for the first time, under controversial plans being discussed by Washington and London.

The US Department of Homeland Security wants to introduce the scheme at airports worldwide, including Heathrow and Manchester, to reduce the risk of Islamic State terrorists flying to America.

Guards from Customs and Border Protection would carry out immigration and customs checks before passengers board.

They would be given diplomatic immunity so they could not be prosecuted for any crime committed on British soil.