Opponents argue that Jesus did not require celibacy from his apostles, that sexual repression has led to the sex abuse scandals currently racking the church and that celibacy has been responsible for the dwindling numbers of young men taking up the vocation.

Sister Chris Schenk of the Ohio-based Catholic reform movement Futurechurch believes that celibacy should be made optional.

"Around the world there is a severe shortage of Catholic priests and over 50,000 churches have no pastor," she said. "While the number of Catholics is rising, the number of priests is in decline -- mandatory celibacy can deter quality candidates from entering the priesthood.

"According to the Vatican yearbook, between 1975 and 2010 the world's Catholics increased by 59% from 709.6 million to 1.96 billion, but the number of priests increased only 1.8%.

"In 1975 there were 404,783 priests worldwide compared with 412,000 now. Forty-six percent of the world's priests are in Europe but only 24% of Catholics live there ... and the number is diminishing."

It seems her view may be supported by a majority of American Catholics.

According to a survey of American Catholics by the Pew Research Center taken after Pope Benedict announced his resignation, 58% of congregants favored allowing priests to marry. Even so, the figures showed the divisive nature of the debate: Of those who attend Mass regularly, only 46% supported marriage for priests while 66% of those who attended less regularly supported marriage.

One former seminarian, who did not want to be named because he is still active in the church and not authorized to speak publicly, told CNN the vow of chastity was one of the chief reasons he dropped out of the vocation.

"I had strong issues with celibacy and, at that time, wanted the freedom to get married and didn't know why there could be Lutheran pastors that led perfectly normal family lives and also ran their congregations.

"I certainly understood the celibate side to priesthood and had a certain respect for it -- strangely I still do -- but I just felt that you should be given options."

He said the diocesan college he attended in the United States -- a type of minor seminary -- was designed to prepare students for their commitments at major seminaries if they decided to continue their studies.

"They were obviously making changes from the middle of the century -- in the '30s, '40s and '50s - when the seminaries were packed full, but probably after the whole peace revolution and the sexual revolution guys obviously started having a lot of second thoughts," he said.

He said he saw little evidence of the kind of sexual abuses that have recently come to light and derailed the Catholic Church.

"When you're young, growing up in a big, serious Catholic family - and I went to a Catholic grade school, I was essentially raised, socialized and educated by nuns and priests - that has a very deep impact especially if they're good role models.

"I never had any sleazy nuns or priests when I was growing up, at least none that I knew about," he said. "When you've got such good role models, both nuns and priests, who are celibate, that makes a big mark on you."