Inga-Britt Ahlenius, the UN's former undersecretary general, speaks at UN headquarters in New York on Jan. 10, 2008. (Mark Garten, United Nations/Associated Press)The departing head of the agency that battles corruption in the United Nations issued a scathing assessment Tuesday of Secretary General Ban Ki-moon's record on accountability.

In a confidential memo obtained by The Associated Press, outgoing Undersecretary General Inga-Britt Ahlenius accuses Ban of systematically undermining her authority and weakening the UN's oversight functions so much that it is becoming irrelevant.

"There is no transparency, there is lack of accountability" under Ban's leadership, Ahlenius wrote. The undersecretary general stepped down from a five-year term as head of the Office of Internal Oversight Services last week.

Ban caused "damage to the integrity of a core process" at the UN by blocking her from filling vacant posts and taking other steps that undermined her tenure as head of the Office of Internal Oversight Services, she said.

"Rather than supporting the internal oversight which is the sign of strong leadership and good governance, you have strived to control it which is to undermine its position," the former Swedish auditor general wrote to Ban.

"I regret to say that the Secretariat is now in a process of decay. It is not only falling apart ... it is drifting into irrelevance."

In Ban's defence

Ban's chief of staff, Vijay Nambiar, said "many pertinent facts were overlooked or misrepresented" in Ahlenius' memo, which was first reported on by the Washington Post.

"This secretary-general, like his recent predecessors, has had to strike a balance between acting as a chief administrative officer of the United Nations on the one hand, and providing truly global leadership on the other," Nambiar wrote in a response to the Post that was later released to the AP by Ban's office.

Nambiar said Ban blocked Ahlenius from hiring her choice to head the investigation division.

He did so in the belief that it was "not an interference with the independence of [Ahlenius], but a correct action by the secretary-general to ensure that the requirements of the relevant rules and policies to which OIOS is subject are adhered to," Nambiar said.