Described by Foreign Office sources as an "extremely serious breach of security", the unprecedented posting of the names will mean that some agents in the field abroad will have to be brought back to Britain. Their local contacts could also be at risk. Last night the Foreign Office said that "hundreds of people" were affected by the release of the names.
Amongst the 117 names on the list - seen by The Independent - are a number of officers whose identities have neverbeen made public. Others have retired and some are said to have no links to the service.
People named as MI6 officers, alongside details of their postings overseas, include: the son of a former Tory cabinet minister; a Cambridge academic described as a recruiter for the service; a figure involved in last year's "arms to Africa" affair; and embassy officials in Washington and Moscow.
The Foreign Office said last night a contingency plan had been launched to protect officers and their contacts who were in danger as a result of the publication. It said Internet providers had "voluntarily" taken the list off the web.
It is understood, however, that an American magazine specialising in security issues intends to publish the list today.
Last night a Foreign Office source said officials at Vauxhall Cross, MI6's headquarters in London, were taking the matter extremely seriously. "This is not like the Philby scandal in the 50s but this is the largest number of names of agents ever released."
Just who disclosed the information remained unclear. The finger of blame was last night pointing at the renegade former MI6 officer, Richard Tomlinson, a 37-year-old Cambridge graduate who is living in exile in Geneva after serving a six-month sentence for breaching the Official Secrets Act.
Last night he insisted he was not responsible. However, in the weeks leading up to the posting of the names on the Internet on Tuesday, he had threatened to name MI6 officers as part of his battle with the service over his dismissal in 1995, allegedly for being a "loose cannon".
As a result the intelligence service had drawn up a contingency plan to safeguard those officers considered at risk.
A Foreign Office source said officials were concerned that because MI6 takes a leading role in tackling serious and organised crime, officers could be at risk from drug dealers, arms smugglers and other criminals.
"These days even an unfriendly government is not going to go around shooting your agents. The risk is from the sort of people who wouldn't think twice about killing someone," said the source.
The existence of the information is understood to have been discovered by government officials - possibly based at the intelligence service's listening centre, GCHQ, in Cheltenham, Gloucestershire.
The list includes some of the most senior officers in the SIS.It gives every appearance of being correct, although it is slightly out of date. This could reflect the fact that Mr Tomlinson - if indeed he posted the site - left the SIS four years ago.
Last night Scotland Yard confirmed it was investigating the release of the names, which is considered a breach of the Official Secrets Act.
Internet service providers have also been warned that if they release any further names they would face prosecution.
The Foreign Secretary, Robin Cook, yesterday told the daily Ministry of Defence briefing on the Kosovo crisis that "not all the names" on the list had a connection with the SIS.
"Nevertheless, the release of any such list, however inaccurate it may be, is a deeply irresponsible and dangerous act," he said.Reuse content