(By Christopher Livesay) Rome, July 25 - The Vatican prelate arrested for alleged involvement in a bid to bring 20 million euros into Italy illegally has written to Pope Francis to say he is innocent, pointing the finger at his bosses and the cardinals who he says protected them. "I never laundered dirty money, I never stole, I tried to help someone who asked for help," Mons. Nunzio Scarano wrote in a letter from Rome's Regina Coeli prison dated July 20 and made public Thursday. "I have documentation that proves my honesty and my battles against the abuse of my secular superiors, covered up by some senior cardinals". Scarano, who until recently led a key Vatican accounting unit, was arrested in June in a probe over allegations he conspired with a former Italian spy and a financial broker to try to secretly repatriate the cash, allegedly the fruit of tax evasion by a family close to the prelate. The prelate, from the port city of Salerno near Naples, had been suspended a month before his arrest from his job as head of analytic accounts at the Holy See's asset-management agency APSA after being named in a separate probe into receiving money in Salerno. Police reportedly started sifting through his assets because of his suspiciously large financial holdings and artistic trove. He was arrested June 28 on suspicion of planning to elude customs controls along with Giovanni Maria Zito, a recently transferred agent in the AISI domestic intelligence agency, and financial broker Giovanni Carenzio. Police said Scarano and Zito set up a private jet to fly the cash for three Salerno-based shipowner brothers, the D'Amicos, whose family was friendly with Scarano. Zito is suspected of getting 400,000 euros for arranging cover for the flight, which never took place. The prelate has told prosecutors he "acted in good faith" and was only "trying to do a favour for the D'Amicos". The Vatican has said it would cooperate "fully" with the probe. The case has come as a blow to the pope who, in one of his final orders of business before heading to Brazil on his first international papal visit Monday, set up a new commission on the economic and administrative structure of the Holy See. Last month he set up a separate commission to oversee the Vatican's scandal-hit bank, the Institute for Religious Works (IOR). The final year of his predecessor Benedict XVI's papacy was overshadowed by his butler leaking to the media confidential church documents, which included allegations of corruption in Vatican contracts. The Vatican has made a series of moves to show greater transparency in the financial transactions that take place in the city state since Jorge Mario Bergoglio, formerly the Jesuit archbishop of Buenos Aires, became Pope Francis in March. The pontiff is reportedly keen to remove stains from IOR's reputation and get the Vatican onto the 'white list' of countries with unimpeachable credentials by working with the Council of Europe's Moneyval anti-money-laundering agency. Scarano's letter painted a picture of himself as not only a victim to Vatican corruption, but as a reformer sympathetic to the pope's same goals: "I just hope to be able to deliver secretly my sheaf of (evidence) that powerfully reinforces (the pope's) great and courageous actions to finally reorder the sad administrative, economic and financial state of the Holy See and all the pertaining and related abuses".