Pope Benedict XVI has returned to traditional Vatican voting rules for the election of the next pope, requiring two thirds of the cardinals in the conclave to agree on a candidate.

The new voting rules were outlined in a one-page document released in Latin on Tuesday. While they could make naming a successor a lengthier and more difficult process, the traditional rules would ensure that the successful candidate enjoyed a broad consensus of support among the cardinals.

The document, a form of papal decree called a "motu proprio", reverses the changes made by Pope Benedict's predecessor, John Paul II, who opened the way for a pope to be elected with only a slight majority in the event of a deadlock after 33 rounds of balloting.

``It would seem that Pope Benedict wants to ensure that whoever is elected pope enjoys the greatest possible consensus,'' the Vatican spokesman, the Rev Federico Lombardi, was quoted by The Associated Press as saying.

Pope Benedict, the former Cardinal Joseph Ratzinger, was reportedly elected as pope after just four ballots on 19 April 2005.

In his decree, Pope Benedict points towards a run-off vote between the top two candidates in the event of stalemate after 33 rounds of voting.