Before the conclave, Benedict XVI ordered an inquiry into Vatican leaks. Now the men who will choose his successor demand its full disclosure

It is known throughout the Vatican as the Relatio (Narration). It is contained in two stiff, unmarked red folders and runs to around 300 pages. Lying in a safe in the papal apartments of the Apostolic Palace overlooking St Peter's Square, it will be at the forefront of the minds of the 115 cardinals who on Tuesday are to file into the Sistine chapel to start the conclave that elects the next pope.

In the Relatio are the findings of three cardinal-detectives, appointed last year by ex-pope Benedict XVI to investigate the leaking of documents from his study. The cardinals, headed by a Spanish member of the Opus Dei fellowship, Cardinal Julián Herranz, discovered the main source of the leaks – the pope's butler, Paolo Gabriele.

But they found a great deal else – and some of it is reportedly extremely compromising. According to one unconfirmed report, they stumbled on a gay sex ring in the Vatican, some of whose members had been blackmailed.

Already dismayed by the blunders that marred Benedict's papacy, many of the cardinals in Rome to elect his successor are seething with resentment towards the Roman Curia, the intensely secretive and predominantly Italian bureaucracy that administers the Catholic church.

"The anti-curial – and anti-Italian – feeling is almost palpable," said a source close to their deliberations.

On the first day of last week's pre-conclave discussions, known as general congregations, three cardinals demanded that Herranz circulate the Relatio. For Massimo Franco, author of a recently published book on the protracted crisis rocking the Vatican, this was more than just prurient curiosity. "The cardinals must vote with a clear view of the situation in the Vatican," he said. "Otherwise, they could be voting for a pope who is accused of wrongdoing in the report. If that comes out afterwards, it would cause mayhem."

Neither can they avoid that risk simply by voting for a pastoral cardinal – one who is an archbishop in his own country. Most have at least one seat on the committees that oversee the work of the Vatican's various departments and they are frequent visitors to Rome. Innocently or otherwise, one or more could have been linked to events detailed in the Relatio.

Yet Herranz's reaction was to hold out, apparently signalling that Benedict ordered that the report be kept for his successor. Many in and around the Vatican interpreted his reaction as confirmation of something already becoming apparent – faced with demands for transparency, the departmental satraps of the Curia were closing ranks.

Indeed, the approach to this conclave has brought about what many in Rome would deem a miracle: an apparent, if temporary, healing of the breach between the Vatican's two most renowned adversaries, Cardinal Tarcisio Bertone, the secretary of state, and his predecessor, Cardinal Angelo Sodano. As a result, a conclave that had been billed as a trial of strength between the two men is shaping up instead as a battle between the "Romans" and invading "Barbarians".

The first group includes the power-brokers in the Vatican and their allies, many of whom are Italians; the second faction, bent on shaking the Curia to its foundations, is led by cardinals from the United States and Germany.

But to see it as a contest between conservatives and liberals would be a mistake: after eight years of Benedict XVI and 27 of John Paul II, there are precious few liberals among the cardinals.

The most obvious sign of the Barbarians' drive for greater transparency was visible last week on the Janiculum, the hill south of the Vatican that at this time of year offers sublime views to the snowy Apennines. In the North American college, the US cardinals attending the general congregations gave daily media briefings in which they managed to shed light on the process without breaking their duty of confidentiality or contradicting the official account of the pope's spokesman, Father Federico Lombardi.

But on Wednesday they were made to shut up in a move that had as much to do with the looming face-off in the Sistine chapel as with media relations. The pretext was a report in the Italian newspaper La Stampa on the previous day's proceedings that certainly did not come from the Americans' press conferences.

Initial skirmishing, then, went to the Romans. But the battle itself has yet to be fought, even if there are indications already of who initially will champion each side. The choices are deceptive. The Romans have, for the moment, put their faith in a cardinal who is neither Italian nor curial: the archbishop of São Paulo, Odilo Scherer. Though an "out-of-towner", Scherer is well versed in the ways of the Vatican. The extent of the curial insiders' trust in him is shown by his appointment to the commission that oversees the Vatican bank. Meanwhile, the Barbarians' hopes have coalesced around an Italian, Angelo Scola, archbishop of Milan. A disciple, like Benedict, of the Swiss theologian Hans Urs von Balthasar, Scola is intimately linked to the conservative fellowship Communion and Liberation. Temperamentally, though, he is unlike the retiring Benedict and could vigorously wield the new broom the Barbarians would like to see sweep through the Vatican. He is handicapped by his association with Communion and Liberation, which has recently been tarnished by a corruption scandal in Lombardy, the region around Milan. And, according to someone present, Scola made a speech to the general congregation that was felt to be rather too electioneering.

The Barbarians have two advantages. One is money; the Americans and Germans between them provide much of the cash that keeps the Vatican afloat. The other is the US contingent's apparent unity of purpose.

The Romans, on the other hand, seem to have maths on their side. Of the 115 cardinal-electors, 39 hold – or have held – top curial positions. Another nine are Italians outside the Vatican. Some do not share the Curia's instinctive aversion to transparency, but there are others in the field who do. It is among the "floating voters" of the emerging countries that the deciding votes are likely to be cast.

"The Curia feels itself to be very strong," said Massimo Franco. "Under threat, but strong."