The government has warned all airlines not to allow NSA whistleblower Edward Snowden to board flights to the UK as it was"highly likely" he would be refused entry.
The Home Office has issued a letter to airlines around the globe advising them not to let Snowden board any flights bound for the UK.
The alert, dated Monday on a Home Office letterhead, said carriers should deny Snowden boarding because "the individual is highly likely to be refused entry to the UK".
Associated Press has seen a photograph of the document that was taken today (14 June) at a Thai airport. A British diplomat confirmed that the document was genuine and was sent out to airlines around the world. A Thai airline also confirmed the alert had been issued.
The letter was issued to all airlines which operate flights into the UK. Failure to comply could carry a fine of up to £2,000. The diplomat said the Home Office would view Snowden's presence as detrimental to the "public good".
Despite the warning, it is highly unlikely that Snowden would chose the UK as his next destination because of its long-standing extradition agreement.
The controversial UK-US extradition treaty of 2003 allows the US to extradite people to the US for offences committed against US law - even though the alleged offence may have been committed in the UK by a person living and working in the UK at the time.
In this case it is assumed that Whitehall would agree immediately to extradite Snowden to the US because the crime he is alleged to have committed took place on US soil and against the US government.
He has not been charged with any crimes but reports suggest that is likely to change shortly.
Snowden, 29, revealed himself on 9 June as the source of top-secret documents about the US National Security Agency (NSA) surveillance programme - known as Prism - that were published by the Guardian and Washington Post.
He was in Hong Kong when he revealed his identity, although on Monday he checked out of the hotel he had been staying in since 20 May and his current whereabouts are unknown. However, in an interview with the South China Morning Post , Snowden said he was still in Hong Kong and would leave only if he was asked to.
He added: "People who think I made a mistake in picking Hong Kong as a location misunderstand my intentions. I am not here to hide from justice, I am here to reveal criminality."
The British alert was issued by the Risk and Liaison Overseas Network, part of the UK Border Agency which has staff in several countries identified as major transit points for inadequately documented passengers.