By Silvia Aloisi and Paolo Biondi

ROME, May 30 (Reuters) - An Italian journalist behind a leaks scandal shaking the Roman Catholic Church denies Vatican accusations he is a criminal and says he was only doing his duty to uncover the truth.

Gianluigi Nuzzi's book, alleging corruption and conspiracies among cardinals in a Vatican struggle for power, has led to a hunt for informants in the Holy See and the arrest of Pope Benedict XVI's butler, one of the people closest to him.

"My job is to find and publish news, it is my ethical duty. These documents reveal the secrets of the Vatican but there is nothing in the documents that threatens the security of that state," Gianluigi Nuzzi told Reuters on Wednesday.

He spoke as the pope denounced what he called false media coverage of the scandal, which his aides have branded a brutal, personal attack on the ageing pontiff.

Nuzzi's book "His Holiness: The Secret Papers of Benedict XVI" contains a trove of private Vatican correspondence, including documents alleging cronysm and corruption in infrastructure contracts with Italian companies, conspiracies among cardinals and clashes over management at the Vatican's own bank, the IOR.

He described cloak-and-dagger meetings with paranoid sources to get the information in the book, which look like they are straight from the pages of a Cold War spy novel.

Nuzzi said the book, which hit the stands last week and is selling out in Rome, is based on conversations with more than 10 Vatican whistleblowers, who have been referred to in the Italian press as "crows", a pejorative term for informants.


"DOVES, NOT CROWS"

He said one whistleblower told him he was part of a group of about 20 informants.

"They are not crows, they are doves who wanted to shed light, clean their air," Nuzzi said.

"These are not people who regularly gave information to newspapers. Clearly there was an accumulation of things that they did not understand or could not bear. If the image of the Vatican that emerges is negative, it is not my fault, it is because of what is written in the documents."

Nuzzi, 42, refused to say whether Paolo Gabriele, the butler now being detained by the Vatican gendarmerie, was among his sources, nor whether they included any cardinals.

"I received a lot of documents from a lot of people, sometimes by the very people who had written them. All of my sources were perfectly aware of what would happen," he said.

The Vatican has not denied the authenticity of the documents, copies of which are reproduced in the book.

An investigative journalist who had already exposed alleged corruption at the Vatican in a 2009 book, Nuzzi said he did not pay anything for the documents and that his sources told him they had not been given any money to leak them.

In a letter from 2011 published in the book, Archbishop Carlo Maria Vigano - then the deputy governor of the Vatican City - wrote to Pope Benedict arguing that transferring him to another post would undermine his efforts to fight "corruption and abuse" in various Vatican offices.

Despite his plea, Vigano was moved to become the Holy See's ambassador in Washington.

Another letter was written by Ettore Gotti Tedeschi, the president of the Vatican bank, to Monsignor Georg Ganswein, the pope's secretary.

In the letter Gotti Tedeschi, who was dismissed last week, defended himself after he and another Vatican official were put under investigation by Rome magistrates in 2010 for failing to explain the origin of 23 million euros which the Vatican bank transferred between accounts it held in two other banks.

Nuzzi's book describes the secretive meetings he had with his main source, codenamed "Maria". After being tested during by a string of intermediaries, he was driven round the same Rome streets for an hour before reaching an empty apartment.

There, in a room furnished with a single plastic chair, he met "Maria", whom he describes as a devout Catholic who has worked at the Vatican for nearly 20 years and who began setting aside documents after the death of Pope John Paul in 2005.

After the butler's arrest, other alleged informants told newspapers he was a scapegoat in a struggle for power in the Holy See that went much higher and wider than him.

Nuzzi said his book has certainly exposed "vulnerabilities and clashes" within the Vatican but that it was not an attack on the pope or the Church.

"There is not a single word in the book against the pontiff," he said. "The Vatican's workings are slow but inexorable." (Reporting By Silvia Aloisi; editing by Barry Moody and Angus MacSwan)