Charles Scicluna
Auxiliary Bishop of Malta Monsignor Charles Scicluna is congratulated by fellow bishops during his ordination ceremony at St John's Co-Cathedral in Valletta (Reuters)

An influential Catholic bishop, who fought paedophilia and sex abuse in the Church, has given new strength to claims that Pope Benedict XVI resigned over power struggles and infights in Vatican.

Monsignor Charles Scicluna, 53, said Benedict stepped down to make way for a stronger pope, able to get a grip of Vatican power struggles.

Scicluna told Il Correire della Sera: "He [Benedict] wanted to leave room for a person able to take the reins of the situation. This is a message cardinals [voting to elect a new pontiff] can't neglect."

Scicluna was appointed promoter of justice in the Congregation for the Doctrine of the Faith, the Vatican office tasked with overseeing Church's integrity, and to asked in 2002 by then cardonal Joseph Ratzinger to investigate claims of sex abuse by clergymen.

An outspoken critic of the Vatican's murky handling of sex abuse cases, Scicluna was appointed auxiliary bishop of the Roman Catholic archdiocese of Malta in 2012.

The promotion was suggested by Vatican secretary of state Tarcisio Bertone and read by analysts as a way to exile the bishop from Rome.

His radical views had reportedly upset the same lobbies that were resisting Benedict's efforts to enhance transparency in the Holy See.

Italian media reports have claimed that Benedict opted to resign after reading a damning dossier on the Vatileaks scandal that revealed rivalries within the Church had undermined him.

The report was drawn up by three cardinals Benedict had tasked with investigating the leak of internal Vatican documents that were handed by the Pope's personal butler - Paolo Gabriele - to Italian journalist Gianluigi Nuzzi.

"Nuzzi's book has created a wave that has carried many people away." Scicluna said. "I've always maintained he [Gabriele] couldn't possibly have acted alone but did so on behalf of a third party, which is yet unknown to us."

The conclave that is to identify a successor for Benedict, who officially stepped down because of old age and declining strength, is due to begin on Tuesday.