Following former cabinet secretary Clare Short's claims that the UK spied on Kofi Annan, BBC security correspondent Frank Gardner looks at the legitimacy of intelligence eavesdropping.
Ms Short said she saw transcripts of Kofi Annan's conversations
Q. How has the government reacted to the allegations?
Officially the government is staying tight-lipped, but people I've spoken to behind the scenes are rather surprised at all the fuss about this.
They point out that there is a great difference between bugging - in the sense of planting a microphone under someone's table or putting a device in a telephone - and simply hoovering up conversations that are in the atmosphere, which is what they say lots of countries do.
Q. Are these sources confirming Clare Short's claims?
They're not confirming or denying that Kofi Annan was eavesdropped on.
But they're saying that if it was true, then it would be perfectly legitimate to simply have a listening station in Yorkshire pulling material down from the airwaves.
Q. Who would be behind any eavesdropping of Kofi Annan?
If the allegations are true, it would most likely be the work of GCHQ, the government's listening station at Cheltenham.
It uses satellite and electronic intelligence gathering to eavesdrop on communications all over the world.
GCHQ's operations are regulated by parliament's Intelligence and Security Act of 1994.
Q. How legal is this sort of intelligence gathering?
My government sources say it is legal.
They are saying everybody does this, that the British UN mission in New York is the target of other people trying to eavesdrop on it.
They're saying that this is really a bit of a storm in a teacup, that it's not the same as sort of planting a little microphone on somebody's lapel.
The Foreign Office says: "GCHQ and MI6 never act outside the law, neither here in Britain, nor abroad."
But there is some debate about this.
Malcolm Shaw QC, Professor of International Law at the University of Leicester, said: "It's not legal to bug foreign diplomats, certainly not without their consent.
"With regards to the United Nations this is covered by the UN headquarters agreements as well as general diplomatic law and it is certainly not legal."
The UN also says it is illegal.
Q. How likely was any transcript of a conversation in Kofi Annan's office seen by Clare Short to have been gleaned by UK intelligence agents?
Government sources are saying that the idea that America would ask Britain to do this on US soil is rather extraordinary.
They are saying the Americans are incredibly protective about what goes on in the US and it would be very unlikely that they would ask for another country - even as close an ally as Britain - to do it for them.
That's what I'm being told unofficially.