British "bugging" Kofi Annan?

[Tuor of Gondolin]

Just heard an odd report on PBS radio. A former Labour cabinet member said T. Blair's Government was spying on U.N. Secretary General- apparently related to the American-British invasion of Iraq, and Blair's response seemed to essentially confirm the charge.
To coin a phrase: "It's worse then a crime, it's a mistake."
What possible gain could there be to make up for the obvious downside if Blair's government was caught doing this? Do they think the Secretary General was scheming against the invasion or had some sort of secret information about Iraq defenses? It seems quite odd.