The Vatican bank is checking the account of every client, including Holy See employees, in a campaign to eradicate any money-laundering.
the Vatican's financial watchdog said last week it was investigating six possible attempts to use the Holy See to launder money in 2012.
In an interview published in Corriere della Sera on Friday, Ernst von Freyberg said the Institute for Works and Religion - the bank's formal name - was reviewing each of 18,900 clients to verify their right to an account and bare any suspicious aspects.
He said he IOR was examining about 1000 accounts a month to pinpoint owners and (establish) who has signature authority.
"This is a system of zero tolerance: No suspect transactions, no improper clients and a willingness to contest anyone who is involved in improper activities, even if they are our own employees," he said.
The bank mainly handles funds for Vatican departments, Roman Catholic charities and orders of priests and nuns worldwide but has been used improperly by third parties in the past.
The Vatican is trying to meet international standards on fighting terrorism financing, money laundering and tax evasion. It will present a progress report in December on recommendations by Moneyval, the European anti-money laundering committee.
von Freyberg was appointed in February to replaced Ettore Gotti Tedeschi, who was fired last May.
The Vatican bank's worst scandal was in 1982 when Roberto Calvi, known as "God's Banker" because of his links to the Vatican, was found hanging from Blackfriars Bridge in London.