Catholic cardinals will start their conclave to elect a successor to Pope Benedict on 12 March.

After five days of closed-door debate, the prelates decided to begin their secret ballot in the Sistine Chapel next Tuesday afternoon.

A total of 115 elector-cardinals, all aged under 80, are expected to take part in the elaborate ritual, which will continue until one man receives at least a two-thirds majority, or 77 votes.

The cardinals are likely to hold just one ballot on the first day and up to four ballots each day thereafter.

Benedict was elected in barely 24 hours in 2005.

His predecessor, John Paul II, became pope after eight rounds of voting spread over three days in the 1978 conclave.

The cardinals have made clear they want another quick conclave this time to make sure they can all return to their dioceses in time to lead Easter celebrations.

Cardinals were in the past locked into areas around the Sistine Chapel, famed for its Michelangelo frescoes, and not allowed out until they had chosen a new pontiff.

But the rules changed before the 2005 conclave and the prelates now get to reside in a comfortable Vatican hotel while they are not voting in the chapel itself.

Vatican spokesman Father Federico Lombardi said the cardinal electors would draw lots to see which rooms they would sleep in, with all external contact, including emails and telephone calls, forbidden.

Jamming devices will also be installed around the Sistine Chapel and the hotel to stop outsiders eavesdropping and to prevent mobile phone usage in the area.

One senior churchman is believed to have let slip to friends in Germany that Cardinal Joseph Ratzinger had been elected pope in 2005 before the crowds waiting in the nearby St Peter's Square were informed.

Meanwhile, the Association of Catholic Priests in Ireland has urged that Pope Benedict's successor should dispel the climate of fear and repression in the Church.

It has also called on the new pope not to reappoint any of the Vatican's departmental leaders but new people who would introduce new ideas and attitudes.

The association also calls on the new pope to fully implement the second Vatican Council's programme for renewal.

Its statement praises Pope Benedict's resignation for prompting a growing realisation of the need for church reform and renewal.

The association has seen Rome silence members for dissent and urges the new pontiff to dispel what it calls "the climate of fear and repression that has dogged the Church for some decades".

It says it should replace it with one of "openness and tolerance" in which the institution's many serious difficulties can be discussed.