A Catholic organisation advocating women's ordination has organised a conference days before Pope Francis is due to speak in Philadelphia.

The Roman Catholic Church holds that Priesthood is a role solely to be held by men, however there is a growing movement of Roman Catholic women who would beg to differ.

While Pope Francis has been lauded as progressive in many respects, his treatment of women is his 'blind spot', according to Miriam Duignan a leader of The Women's Ordination Worldwide (WOW).

Their conference has been scheduled just before the World Meeting of Families, where Pope Francis is speaking, to make it a "call to action for Catholics and to get Francis' attention". "We want more Catholics to see women's rights as a justice issue," she said.

The Pope has said the topic of ordination of women is a closed book.

"I readily acknowledge that many women share pastoral responsibilities with priests, helping to guide people, families and groups and offering new contributions to theological reflection," the Pope wrote in in his apostolic exhortation, Evangelii Gaudium. 

Despite this, he maintains that "The reservation of the priesthood to males, as a sign of Christ the spouse who gives himself in the Eucharist, is not a question open to discussion." 

Women are told they cannot be priests because they do not physically resemble Christ and therefore cannot stand on the altar to represent Him to the Church.

WOW says that the denial of female priesthood on physical grounds is damaging. 

"Why can't women be priests? Because you failed to meet the selection criteria of God because you are a man," said Duignan.

"We cannot allow this to continue to be said to 1.2 billion Catholics around the world."

Women are often told that if they feel they are called to priesthood, they are in fact discerning wrongly, she added.

This position is inherited from the Pope's predecessors. In 1994 John Paul II declared that any woman who sought ordination would be excommunicated. Pope Benedict, then Cardinal Joseph Ratzinger, ruled that the teaching on an exclusively male priesthood had been "set forth infallibly."

The Catholic Church teaches that it has no authority to allow women to become priests because Jesus Christ willingly chose only men as his apostles when he instituted the priesthood at the Last Supper.

Proponents of a female priesthood say Jesus Christ was only acting according to the customs of his times.

One group that is part of the conference has taken matters into their own hands; Roman Catholic Womanpriests is a group which has ordained 188 women into priesthood.

Caryl Johnson calls herself a priest, but technically she was excommunicated when she was ordained by Roman Catholic Womanpriests.

Johnson said she struggled for more than three decades with the ban on female ordination. She tried to do all that she could within the limitations set on women in the Catholic Church, but she said it was not enough.

"I had a decision to make," said Johnson. "Am I going to follow the spirit of God and do what God asks no matter what the cost? Or am I going to follow a rule?"

The attempted ordination of a woman was determined a "grave crime" officially by the Catholic Church by Pope Benedict and results in excommunication.

Although officially no longer part of the Roman Catholic Church, women such as Johnson are keen to keep their Catholic identity and are fighting for mainstream ordination simultaneously.

"You are born into Catholic faith – it is such a strong faith wrapped up in identity and culture that it isn't just a matter of boycotting it" in order to move forward, according to Duignan.

"It is a very powerful church and a very powerful message – I cannot, as someone who loves my church and cares deeply about the treatment of women, stay silent.

"You cannot work towards equality whilst allowing the world's largest faith to say that women are misbegotten males."

While critiquing Pope Francis' approach to women, Duignan said she is hopeful there is potential for progress.

"The good thing is that he does occasionally have these AHA moments when he does change his mind on things. He is often persuaded by a personal encounter."

Her hope is that he might meet one of the women who feel called to priesthood and see the reality that they would be a "perfect priest who leads people in the divine the way Jesus would have hoped."

A recent poll by Pew Research Centre found that 58 per cent of Catholics believe the Church should ordain woman. This is in accordance with WOW's belief that many parishioners believe women should be priests, but do not voice that opinion since it was made an officially banned topic in 1994 by Pope John Paul II.

Although WOW was denied an official seat at the conference, members of WOW will be attending The World Meeting of Families not to protest, Duignan says, but as parishioners who love their church and want to work within it to bring about change.

"We are not a fringe group who are trying to bring down the Catholic Church, we are all part of the Catholic Church."

The WOW conference entitled 'Gender, Gospel and Global Justice' is being held in Philadelphia on 18-20th September