Pope Benedict will be confronted by posters on London's famous red buses during his trip to the British capital next month which will call for the ordination of women priests.
Protests are planned throughout his four-day trip to England and Scotland, the first papal visit since John Paul II's pastoral visit in 1982 and the first-ever official papal visit to Britain.
One group of women, Catholic Women's Ordination (CWO), will have its message plastered on the side of the buses as they travel along key routes, including past Westminster Hall, at the Palace of Westminster, where the pope is set to deliver a speech to Britain's civic society on Sept. 17.
The group has paid 15,000 pounds for 15 buses to carry the message "Pope Benedict - Ordain Women Now!" for a month.
"We do not want to be disruptive, but I think the church has got to change or it will not survive," CWO spokeswoman Pat Brown told Reuters.
"I am quite hopeful at the moment because I think the church is in disarray."
It also hopes to protest outside Lambeth Palace during a meeting between the pope and Rowan Williams, the Archbishop of Canterbury, spiritual head of the Church of England, the Anglican mother church.
Set up in 1993, the CWO describes itself as loyal to the Roman Catholic Church, campaigning from within for inclusivity and the ordination of women.
It was angered by a Vatican document last month which mentioned the ordination of women amid sweeping revisions of its laws against child sex abuse. The Vatican later denied accusations it viewed the two issues as equally criminal.
The CWO has also launched a group "Catholic Voices for Reform" to coincide with the pope's visit to counter "Catholic Voices", a media-friendly group which has the backing of the Bishops' Conference of England and Wales.
They will go head-to-head on controversial matters such as child abuse, women's ordination, married priests, homosexuality and the way the church is run.
CWO will not be taking part in the main demonstration against the pope's visit, which is being organised under the umbrella banner "Protest the Pope", which includes humanists, secularists and gay rights campaigners.
Tens of thousands of Catholics are expected to attend the three major public events in Glasgow, London and Birmingham, with many lining the streets to greet the pope in his Popemobile.