Discontented Anglicans who convert must not become a "sect" within the Roman Catholic Church, a senior Catholic clergyman dealing with church unity has warned.
Anglicans who object to plans for women bishops are considering the Vatican's invitation to become part of a special section - an "ordinariate" - within the church in England and Wales.
Monsignor Andrew Faley, Assistant General Secretary of the English and Welsh Catholic bishops' conference, told the BBC News website that ordinariate members would be expected to co-operate with their local bishop and the life of their local Catholic parish.
"They can't live separate from it... that would be a "sect" approach and that would not be tolerated within the Catholic understanding of the church," he said.
As well as dealing with inter-church relations for the bishops' conference, Mgr Faley is a member of the commission it has set up to "consider the next steps" following the Vatican's publication of an Apostolic Constitution on receiving Anglican converts.
"What it means to be a Catholic is a very important question and a question that anyone considering the ordinariate needs to be seeking answers to," he insists.
"They become members of a Church which has the ministry of the successor of St Peter as its source of unity... unity for Catholics is central to their understanding of the Church."
Meanwhile, much still needs to be clarified about the application of the Apostolic Constitution, says Mgr Faley.
The Vatican document provides that the ordinariate, headed by an "ordinary" with similar status to a bishop, and its parishes would be separate from the ordinary Catholic dioceses and parishes - but with many links to them at national and local level.
Members of the ordinariate would retain "those aspects of the Anglican patrimony that are of particular value". Some media reports have claimed this refers to the practice of allowing priests to marry.
A substantial number of married ex-Anglican priests are already Catholic priests, having crossed to Rome in the years following the ordination of women priests by the Church of England in the 1990s.
But the overwhelming majority of Catholic priests in Britain are required to remain unmarried and celibate.
The Apostolic Constitution, by setting out the procedure for admitting married men to the priesthood within the ordinariate, has revived interest among some Catholics in the question of priestly celibacy within their church.
But Mgr Faley says there is no great change in the offing.
The mechanism for giving a dispensation to married ex-Anglican clergy to become Catholic priests will continue in the ordinariate, he says.
But a man in the ordinariate who wishes to be considered as a priest "would be ordained as a celibate priest; he wouldn't be allowed to marry."
And a married man who has not been an Anglican priest, could he apply? "No," says Mgr Faley, "A married man within the Catholic tradition cannot be ordained; the norm is celibacy."
The Apostolic Constitution allows for a former Anglican bishop to head the ordinariate. If he were married - as are most of the bishops on the Catholic wing of the Church of England - he could not be a Roman Catholic bishop, but could be the ordinary, and a member of the bishops' conference.
Book of Common Prayer
However, Mgr Faley feels: "Within the nature of the bishops' conference as it currently stands it's almost certain that the ordinary of the ordinariate would be a celibate Catholic bishop."
Some commentators might be surprised by the idea that the head of the ordinariate would not be a leader from the present Anglo-Catholic tradition.
"I really don't know," says Mgr Faley. "There is the possibility that he would be - but within the culture of the bishops' conference I think that's highly unlikely."
Another Anglican tradition many commentators have mentioned is the use of the Book of Common Prayer as the framework of church ceremonies.
But many Anglo-Catholic parishes in the Church of England do not use the Book of Common Prayer; they use the Roman Rite, as the Roman Catholics do.
Such congregations might be happier as mainstream Roman Catholics - or staying in the C of E, says Mgr Faley.
The ordinariate will not follow the Roman rite; it will follow "Anglican worship patterns" as approved by Rome following a revision to bring them in line with Catholic teaching, he anticipates.
In fact, says Mgr Faley, "What is meant by 'Anglican patrimony' will have to be explored thoroughly... will need to be very clearly stated and very clearly described."
He does not foresee legal battles over church buildings if groups of Anglicans do decide to convert to Rome in large numbers. Unlike North America, Anglican congregations do not own their own buildings, he says; the Anglican Church's relationship to its property is enshrined in law:
"There's no way in which a parish moving from the Church of England to the ordinariate would be allowed to take its parish property with it. That's just not possible at all."
Sharing an Anglican church building might work in some "very particular" situations, he says, but "broadly speaking I think it's more likely that a parish in the ordinariate for worship purposes would share the local Catholic church or churches."
And another task for the commission, he stresses, is to "maintain a good working relationship which we already have with the Church of England".
The joint search for "the full unity of the Church" carries on, he says: "I think it's quite an important point, really."