Boston's Jim Post has a message for Bishop William Murphy, leader of the Roman Catholic Diocese of Rockville Centre.

"If your purpose in banning Voice of the Faithful meetings on church property is to suggest the group has no right to exist, we're going to contest that," said Post, president of the lay group that is demanding a greater role in church governance in the wake of the priest sex-abuse scandals.

As a result of Murphy's ban, the Long Island chapter of the group has relocated its meeting from a local parish hall at 7:30 p.m. tomorrow to the new Wyandanch Youth Center at 20 Andrews Ave. Founding members of the Boston-based organization will be on hand to show support. And the group has sent a personal invitation to the bishop to attend.

"I wrote him personally to say that I understand that you have said you do not want to recognize Voice of the Faithful ... but nevertheless, we invite you to come to the meeting simply to hear the concerns of the people of your diocese," said facilitator Sheila Peiffer, director of religious education for Sacred Hearts of Jesus and Mary Church in Southampton.

Since Murphy's edict last month, ostensibly because he believes the group is "divisive," he and Post have been de facto adversaries in a national debate about the role of Voice of the Faithful in the healing and future of the Catholic Church in the United States.

In his first detailed explanation of that decision, Murphy last week said he sees his task as bishop is "to serve the unity of the church [and] to protect the church," and that he believed his plans for a diocesan-wide synod in 2007 were the best and the "most inclusive process" to hear lay concerns.

"It is the most grassroots thing you can have," he said of the synod process.

Two other bishops, William Lori of Bridgeport, Conn., and Joseph John Gerry of Portland, Maine, also have barred the meetings on church property, while Boston's Cardinal Bernard Law has refused to accept money the group collected. But several other bishops, such as Nashville, Tenn.'s Bishop Edward Kmiec, have had cordial meetings with members.

Post said he believes Voice of the Faithful, which has grown to more than 30,000 members in more than 40 states, has become the target of a "coordinated campaign of distortion" though it has advocated only three goals: supporting victims of abuse, supporting "priests of integrity" and shaping structural change to allow greater lay involvement.

"We do not advocate the end of priestly celibacy, the exclusion of homosexuals from the priesthood, the ordination of women, or any of the other remedies that some have proposed," he wrote in a letter posted on the group's Web site, www.votf.org. " ... We do promote a full and open discussion about the root causes of the sexual abuse crisis and the remedies that are needed."

Post, a professor at Boston University, said he is troubled by Murphy's response because the former vicar general of the Boston archdiocese knows many of the group's founders. He said Murphy used to celebrate Mass at St. John the Evangelist Church in Wellesley, Mass., where the group began seven months ago.

"We knew Bill Murphy and he knows us," Post said. "He knows we're mainstream Catholics who care deeply about our faith. Just a short while ago, he would have pointed to us as the very models of engaged Catholic laity."

Staff Writer Rita Ciolli contributed to this story.