BRITAIN STORIES/UPDATE3

Lives risked

While he would not comment on the work of Britain's security services, he urged people not to take this as an indication that Ms Short's allegations were true. "I really do regard what Clare Short has said this morning as totally irresponsible, and entirely consistent," he said. "I am sorry that she has said the things that she's said, but she must know, and I think everyone knows, you can't have a situation where people start making allegations like this about our security services. "It is completely irresponsible ... This is a dangerous time for this country and the world. "We need our security services. We need these people who risk their lives for us to feel confident of the strong support and backing right across the political spectrum for what they do. "I give them that strong backing - I think they do a fantastic job. "I really regret the way they have been dragged through the mud over the past few months. It is totally unfair for them ... "People who put them in the firing line like this - I really do not have a great deal of respect for ... "It's just a pity she's done what she's done today because I think it is wrong."

The UK has three main intelligence agencies with a combined budget of just under £900m a year. Between them they run agents, combat internal subversion and identify threats to the UK from abroad.

MI6 had its origins in the Secret Service Bureau before the First World War, as did MI5. Its first leader was Sir Mansfield Cumming, who always signed himself "C", a tradition carried on by his successors. The department falls under the remit of the Foreign Office, and is based in a rather eye-catching building in Vauxhall in London. It was MI6 which supplied much of the information that went into the September 2002 intelligence dossier on Iraq, notably the singled sourced second hand reports that Iraq was able to launch weapons of mass destruction within 45 minutes.

Government Communications Headquarters, set up in 1946, was born out of the wartime code-breakers based in Bletchley Park. Based in Cheltenham GCHQ has two functions, to monitor, intercept and decrypt information from those who pose a threat to the UK and also to keep confidential government information secret. Staffed by civil servants, including skilled mathematicians and linguists, GCHQ comes under the responsibility of the Foreign Office.