The Vatican says it has no comment on a media report that an Italian prelate was transferred to Washington as papal ambassador after he wrote to the pope complaining about corruption in the awarding of Vatican contracts.

The allegation is carried in a report, being televised Wednesday night, by Gian Luigi Nuzzi, author of a 2009 book outlining the shady dealings by the Vatican bank.

A report in Corriere della Sera on Wednesday said Archbishop Carlo Maria Vigano used the term "corruption" in a letter to Pope Benedict XVI to explain the difficulties he faced in his position as secretary-general of the Vatican city-state.

It said the letter was sent March 27 in an extreme attempt to head off his transfer. Vigano was named U.S. ambassador in October.