POPE Benedict XVI is standing down.

Benedict became the head of the Catholic church in 2005 but a Vatican statement said the pope was unable to continue in office due to his age and diminishing strength.

He is 85, and the papacy will remain vacant until a successor is elected.

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The last Pope to resign rather than die was Gregory XII in 1415.

Locally, it was an initiative from Pope Benedict that saw 12 Anglican nuns convert to Catholicism on January 1.

The sisters, who were based at Wantage’s Community of St Mary the Virgin, left to join the Pope’s Personal Ordinariate of Our Lady of Walsingham, set up last year, and were only the second group of Anglican nuns in the country to leave the Church of England for the Roman Catholic Church.

He is the first pontiff to resign in nearly 600 years. The decision sets the stage for a conclave to elect a new pope before the end of March.

The pope announced his decision in Latin during a meeting of Vatican cardinals this morning.

"After having repeatedly examined my conscience before God, I have come to the certainty that my strengths due to an advanced age are no longer suited to an adequate exercise of the Petrine ministry," he told the cardinals.

"I am well aware that this ministry, due to its essential spiritual nature, must be carried out not only by words and deeds but no less with prayer and suffering.

"However, in today's world, subject to so many rapid changes and shaken by questions of deep relevance for the life of faith, in order to govern the bark of St Peter and proclaim the Gospel, both strength of mind and body are necessary - strengths which in the last few months, has deteriorated in me to the extent that I have had to recognise my incapacity to adequately the ministry entrusted to me."

The last pope to resign was Pope Gregory XII, who stepped down in 1415 in a deal to end the Great Western Schism among competing papal claimants.

The pope called his choice "a decision of great importance for the life of the church."

There are several papal contenders in the wings, but no obvious front-runner as was the case when Pope Benedict was elected pontiff in 2005 after the death of Pope John Paul II.