UN Secretary General Kofi Annan

The ex-international development secretary said she had read some of the transcripts of his conversations.

Ms Short said she recalled thinking, as she talked to Mr Annan: "Oh dear, there will be a transcript of this and people will see what he and I are saying."

Downing Street has refused to comment on the claims, made in a BBC interview.

Spies there 'for some time'

Her comments came the day after the dramatic collapse of the trial of GCHQ whistle-blower Katharine Gun.

She had been accused of leaking a secret e-mail from US spies apparently requesting British help in bugging UN delegates head of the Iraq invasion.

The UK in this time was also getting spies on Kofi Annan's office and getting reports from him about what was going on Clare Short Listen to the full Today programme interview

During an interview on BBC Radio 4's Today programme Ms Short said British spies were involved in bugging Mr Annan's office in the run up to war with Iraq.

"The UK in this time was also getting spies on Kofi Annan's office and getting reports from him about what was going on," she said.

"These things are done and in the case of Kofi's office, it was being done for some time."

Legal question

Asked if Britain was involved in this, she replied; "Well I know - I've seen transcripts of Kofi Annan's conversations.

"In fact, I have had conversations with Kofi in the run up to the war thinking 'oh dear, there will be a transcript of this and people will see what he and I are saying'."

There is no need to spy or to go through secret channels Hassen Fodha UN director in Brussels Profile of Clare Short

Asked to confirm if British spies were instructed to carry out operations within the UN on people like Mr Annan, she said: "Yes, absolutely."

Quizzed about whether she knew about this when she was in government, Ms Short responded: "Absolutely. I read some of the transcripts of the accounts of his conversations."

Pressed about whether this was legal, she said: "I don't know. I presume so. It is odd but I don't know about the legalities."

'Tarnished reputation'?

A Downing Street spokesman said in a statement: "We never comment on intelligence matters. Our intelligence and security agencies act in accordance with national and international law at all times."

BBC security correspondent Frank Gardner said that many UN officials always worked on the basis that they were being bugged.

Clare Short has been a thorn in the government's side since she quit

But, he added, "that is not to say that it is acceptable if they are not suspected of terrorism or other crimes".

Hassen Fodha, the UN director in Brussels, said: "The UN works in full transparency. There is no need to spy or to go through secret channels.

"Our information is public and under our rules no other information than is public should be used in our reports."

Tory shadow foreign secretary Michael Ancram was cautious about reacting to Ms Short's remarks, saying: "I think she should be asked why she's saying this now. I don't know what the truth of this is."

'Sensitive matters'

But Sir Menzies Campbell, the Liberal Democrat foreign affairs spokesman, said: "If these allegations are true, they will do nothing for Britain's already tarnished reputation at the UN."

Donald Anderson, chairman of the Commons foreign affairs committee, said "even talking about what passed over" Ms Short's desk "is wholly wrong in principle".

Defence expert Col Mike Dewar agreed, saying she should not be talking about such sensitive matters because they could compromise intelligence sources.

Earlier, Ms Short said enormous pressure was being brought to bear on countries that were not supportive of the Iraq war.

She said Baroness Amos, who was a spokeswoman on international development, had gone round Africa, with people from the British intelligence services "trying to press them".

Political motivation?

"I had to make sure that we didn't promise them misuse of aid in a way that would be illegal," said Ms Short, who was Lady Amos's boss at the time.

The prime minister's monthly media briefing on Thursday is expected to be dominated by Ms Short's revelations and the dropping of the case against the ex-intelligence officer Katharine Gun.

The government has denied claims the move to drop the case was politically motivated.

There has been speculation ministers were worried about the disclosure of secret documents during the trial, particularly the advice from Attorney General Lord Goldsmith about the legality of war.