Rome (AFP) - The Vatican's former auditor general, who resigned without explanation in June, said Sunday he was forced out after his investigations into possible illegal activity hit too close to home.

"Let me be clear: I did not voluntarily resign. I was threatened with arrest," Libero Milone said in an interview conducted with four media outlets including Italy's Corriere della Sera daily.

The auditing whizz, who spent much of his career with the audit firm Deloitte & Touche and was hired to much fanfare in 2015, said high-ranking figures in the Vatican wanted to scupper Pope Francis's financial reform efforts.

"I fear very sorry for the pope. I had a splendid, indescribable relationship with him, but over the last 18 months they stopped me seeing him. Obviously they didn't want me telling him about some of the things I'd seen," he said.

While a non-disclosure agreement prevents him from giving details of the irregularities he uncovered, Milone suggested his troubles began when he hired an outside firm to check whether the computers of his team had been bugged.

When he was hired Vatican officials said he would be "completely independent" and would have the power to look through the books of every department in the tiny city state, reporting only to the pope.

But he was accused of using the outside firm to spy on Vatican officials, Milone said.

"They accused me of having improperly looked for information on Vatican members. I found out they had been investigating me for seven months," he added.

"I was only doing my job".