Mulambo Haimbe said there was an "increasing tendency" by envoys to ignore diplomatic channels, and this could undermine the "spirit of mutual respect".

He did not name anyone but his comments were seen as being directed at the US Ambassador to Lusaka, Michael Gonzales.

Last week, Gonzales called a press conference to announce that the US was cutting $50m (£37m) of health aid to Zambia because of the theft of life-saving medications that the US had provided for patients.

He added that he had decided to go public after holding more than 30 fruitless meetings with senior Zambian officials.

In his response, Haimbe said that addressing the government through the media amounted to interference and was in breach of diplomatic conventions.

"We remain open to addressing any matters of concern through appropriate diplomatic channels," the minister added.

Last week, the US Embassy said it had presented its findings of the alleged corruption to Zambian officials in April last year, and had offered help to stop further theft and to bring the culprits to justice.

However, no action was taken by the Zambian authorities, it added.

On Monday, Zambia's Home Affairs Minister, Jacob Mwiimbu, said that a forensic audit on the alleged theft had been completed and handed over to security agencies for further action.