The first external audit of Vatican finances by an internationally respected accountancy firm has been halted.

In what will be seen as a blow to Pope Francis’ reforms, a letter on 12 April was sent to Holy See departments informing them the work of PricewaterhouseCoopers has been "suspended immediately".

The letter, reported by Crux, was written by Archbishop Giovanni Angelo Becciu, one of the top officials at the Vatican’s Secretariat of State. It explains that any permission to hand financial data to PwC has now been revoked.

Australian Cardinal George Pell, Prefect of the Secretariat for the Economy, had commissioned PwC to review the Vatican accounts, work which had previously been done by an Italian firm. The audit by PwC was the first of its kind and was going to provide a complete picture of Holy See finances, including a valuation of all its assets.

But in his letter Archbishop Becciu said that Cardinal Pell’s instruction for Vatican bodies to co-operate with the firm had been overruled by "superior provision". A spokesman for Pell said he was "surprised" by the suspension of the audit and expects it to resume shortly.

It leaves open the question as to whether this came from the Pope, his advisory body of cardinals or the 15-body council for the economy, led by German Cardinal Reinhard Marx, which oversees the work of Cardinal Pell’s department.

Crux reported that the point of contention by those opposed to the PwC audit was not transparency but a concern over the nature of the contract with the firm.

There has, however, been sustained resistance to the Pope's reforms of Vatican finances which blew up when documents were leaked showing mismanagement of money. Those who leaked them, and the journalists who reported the material, are now being prosecuted in what is known as the "Vatileaks 2" trial.

Cardinal Pell has also become something of a lightning rod for opposition with accusations of dirty tricks being made when the cardinal’s expenses were leaked.

Some of the strongest opposition to Pell’s work has come from within the Holy See's Secretariat of State, traditionally the most powerful body in the Vatican, and APSA (Administration of the Patrimony of the Apostolic See), which manages Vatican assets. Both are believed to have resisted attempts to come under the oversight of Pell's department.

The position of the cardinal, who reaches retirement age of 75 in June, is under pressure - things were made worse for him following four days of uncomfortable cross-examination by an Australian inquiry into clerical sexual abuse.

Pope Francis met with Pell this morning.