However, the project director, Christian Pfeiffer, accused bishops of trying to "censor and control" his work, which aimed to analyse victim statements, the behaviour of molesting priests and reactions by their superiors.

"Trust is essential for such an extensive and sensitive project, as the partners agreed from the outset," Bishop Stephan Ackermann of Trier, the German Church's delegate for issues of sexual abuse, said in a Jan. 9 statement.

"Unfortunately, Professor Pfeiffer's attitude and behaviour toward Church leaders has effectively removed any basis of trust. We regret our attempts at an amicable solution have not succeeded."

Ackermann said the inquiry formed part of the German Church's "comprehensive set of measures," which had included revised guidelines, a telephone hotline and "extensive preventive measures and training opportunities."

He added that a separate project to study forensic reports, based at the University of Duisburg-Essen, had published findings in December, but said the Church would now seek a new research team to take over from Pfeiffer's Criminological Research Institute of Lower Saxony, known by its German acronym, KFN, and would demand repayment of research funds.

In a statement the same day, Pfeiffer said several of Germany's 27 Catholic dioceses had resisted co-operation and had demanded the right to approve his findings.

"Our aim to research abuse by priests has failed because of the censorship and control desired by the Church," said the statement on the KFN web site.

"Scientists cannot be expected to give permanent consideration to whether their formulations or data interpretations exceed the limits of what a project's funders will accept. Their sole obligation is to the truth."

Hundreds of Germans have come forward claiming molestation by Catholic priests and Church staffers since the first case was reported in January 2010 at Berlin's Jesuit-run Canisius Kolleg.

In August 2010, the German bishops' conference released new guidelines for tackling and preventing abuse. The guidelines require all Catholic youth workers to obtain police checks and undergo psychiatric tests and dioceses to appoint independent ombudsmen and experts.

In July 2011, Ackermann said KFN would have access to personnel files from Germany's religious orders and 27 dioceses over the previous decade, as well as files dating back to 1945 from nine dioceses.

Pfeiffer said several dioceses had destroyed documents relating to clerical abuse and reneged on a pledge to co-operate, adding that future researchers should be aware that "signing a contract with the bishops' conference does not provide security."

"The direction blatantly contradicts the interests of victims," Pfeiffer said. "The KFN wishes at least to save the planned victim inquiries and appeals to all Church abuse victims to take part voluntarily in an anonymous questionnaire being drawn up by our institute."

Reacting to the claims, the bishops' conference spokesman, Matthias Kopp, denied that any dioceses had destroyed abuse records or dropped out of the research.

"According to canon law, all relevant documents on offenses in this area must be kept — canon law is stricter here than secular law," Kopp told the German Catholic news agency, KNA. "We might have tried to reach an amicable termination of the contract through mediation, but Pfeiffer was not ready for this."

In December, the German government's special representative for sexual abuse, Johannes-Wilhelm Rorig, criticized a decision by the Catholic Church to close its toll-free hotline for abuse victims at the end of 2012, citing a lack of demand.