The Associated Press news agency reported seeing a document at a Thai airport telling carriers to deny 29-year-old Edward Snowden boarding.
The travel alert with a Home Office letterhead said Mr Snowden “is highly likely to be refused entry to the UK”.
The Home Office would not comment.
According to AP, the alert was issued on Monday by the Home Office’s Risk and Liaison Overseas Network.
The document had a photograph of Snowden and gave his date of birth and passport number, the news agency reported.
It said: “If this individual attempts to travel to the UK: Carriers should deny boarding”.
It went on to warn airlines they may “be liable to costs relating to the individual’s detention and removal” should they allow him to travel. According to the Home Office’s website that charge would be £2,000.
