The claim, formally naming Dr Boutros Ghali for the first time, was made at the start of the first US trial over the UN’s Oil-for-Food scandal.

Prosecutors said that Tongsun Park received $2.5 million (£1.4 million) in cash plus promises of lucrative business deals in return for providing access to Dr Boutros Ghali and at least one other top UN official.

“Tongsun Park has access at the highest levels of the UN. Tongsun Park had his price. Tongsun Park sold his access to the UN. He sold it to the Iraqis,” Michael Farbiarz, a federal prosecutor, told the jury. “Cash by the bagful was sent to the US and doled out to Tongsun Park by an agent for Iraq.”

The prosecution did not allege that Dr Boutros Ghali had received any money during negotiations on the creation of the $64 billion humanitarian programme in 1996. But Mr Farbiarz said that the money Iraq paid to Mr Park appeared to have had its desired effect.

Mr Park, 71, who was born in North Korea, faces up to 12 years in prison on charges that he acted as an unregistered foreign agent for Saddam’s Iraq during and after the creation of the programme.

Prosecutors alleged that Mr Park was recruited by Samir Vincent, an Iraqi-American businessman, who has admitted working illegally for Saddam’s Iraq. Mr Vincent handed Mr Park large sums of cash, prosecutors allege. But it was “just a down payment”, and both men were promised business deals once sanctions were lifted.

The prosecution said it would not try to prove what happened to the money given to Mr Park. But Mr Farbiarz said that about $1 million went into an oil company controlled by Maurice Strong, then a top adviser of Kofi Annan, who is now the UN Secretary-General. Mr Strong called it a normal commercial investment.

Michael Kim, Mr Park’s lawyer, described his client as “just a middle-man in the grand international game of oil and money”. He suggested that Mr Park did not know Mr Vincent was acting for Iraq.

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