Mr Annan is said to be frustrated with the UN's bureaucracy

He said the Security Council - which was split over US and UK plans to invade Iraq - had been shown to be outdated and that the developing world should have a greater say in the future.

Although he described the recent past as a "depressing" period he said he was optimistic about the future.

He said that although the Iraq debate had raised criticisms of the UN, on other issues, such as Iran and Korea, the UN had been seen as an important institution.

1945 structures

"There is a need for reform and I think most governments have accepted and recognised it, and we've talked about it ad infinitum in this building," Mr Annan told BBC Radio 4's United Nations Or Not? programme.

"I think that everybody agrees that the membership and the structure of the Council is a bit anachronistic - it reflects the geo-political realities of 1945, and here we are in 2003 stuck with this structure."

In a way, Iraq has more or less driven home to leaders around the world that the UN is a precious instrument, the UN is important Kofi Annan

Mr Annan said it was unrepresentative that four of the five permanent members of the council were northern, industrial countries.

And he voiced concern about the kind of pressure that can be imposed on small, temporary members particularly from Africa and South America.

In the run-up to the war, both the anti- and pro-war camps employed intensive diplomacy to try to win round smaller members of the council to their view.

Fear of irrelevance

Mr Annan admitted that the entire Iraq crisis was a "depressing period".

"As [former chief weapons inspector Hans] Blix put it, it took us three and half years to gear up and we were shut down in three months.

The same time that the UN was being knocked, the US kept telling Korea, we will take your case to the UN Kofi Annan

"And of course when that happened and the council wouldn't come to a conclusion, there was a sense of what happens to this organisation - but here there was a debate of the UN being irrelevant, the UN going the route of the League of Nations."

However, he added that now the flaws had been exposed, they could be corrected.

"In a way, Iraq has more or less driven home to leaders around the world that the UN is a precious instrument, the UN is important."

He pointed out that while the United States acted alone on Iraq, it was dealing with other issues within UN structures.

"The big countries need the UN too. The same time that the UN was being knocked, the US kept telling Korea, we will take your case to the UN.

"Not only that, on the question of Iran, they say let the [UN] atomic agency and the others come in and do it."