Catholics who have divorced and remarried without first obtaining an annulment must not have sex with their new spouse, a leading Catholic bishop has stated.

In a new set of pastoral guidelines Archbishop of Philadelphia Charles Chaput says divorced and remarried Catholics, as well as all who cohabit without being married, must not have sex if they want to be allowed to receive communion in church.

He also warns that openly gay couples should not be accepted into parish life because they are a danger to the faith of children.

The guidelines come on the back of the two meetings of the Synod on the Family in Rome in 2014 and 2015 and the resulting apostolic exhortation from Pope Francis, Amoris Laetitia.

Chaput was one of the Pope's synod advisers.

Many Catholics had been hoping for leniency from the Church on this issue. The current teaching, which has not changed but is ignored in some parishes, means that even the innocent spouse of an adulterer must be banned from receiving communion if they remarry without an annulment.

Chaput says the Pope's aim in the document is to strengthen existing families and to reach out to those whose marriages have failed, including those who feel alienated from the life of the Church.

"Catholic teaching makes clear that the subjective conscience of the individual can never be set against objective moral truth, as if conscience and truth were two competing principles for moral decision-making," he says.

Since well-meaning people can err in matters of conscience, especially in a culture that is already "deeply confused about complex matters of marriage and sexuality", a person may not be fully culpable for acting against the truth, he says.

Priests should therefore be merciful and adopt a sensitive pastoral approach.

However, Christian marriage, by its nature, "is permanent, monogamous and open to life," he continues.

"But an intimately shared life can also cause stress and suffering. Marital fidelity is an ongoing encounter with reality. Thus it involves real sacrifices and the discipline of subordinating one's own needs to the needs of others."

People who find themselves separated or divorcedand consciously refrain from a new union face no obstacle to receiving communion and other sacraments, he says.

But for Catholics who are divorced and have had a civil remarriage, "Church teaching requires them to refrain from sexual intimacy."

This applies even if they must, for the care of their children, continue to live under one roof.

"Undertaking to live as brother and sister is necessary for the divorced and civilly-remarried to receive reconciliation in the sacrament of penance, which could then open the way to the eucharist."

This means that where pastors give communion to divorced and remarried persons "trying to live chastely", they should do so in a manner that will avoid giving scandal or implying that Christ's teaching can be set aside, he says.

Care must also be taken to avoid "the unintended appearance of an endorsement of divorce and civil remarriage", he warns.

This means divorced and civilly remarried persons should be barred from positions of responsibility in a parish such as serving on the parish council and also they should not be allowed to carry out any liturgical ministries or functions, such as reading from the Bible or adminstering communion.

"This is a hard teaching for many, but anything less misleads people about the nature of the Eucharist and the Church," Chaput says.

Cohabiting and gay couples should also live without sex, he argues.

"Two persons in an active, public same-sex relationship, no matter how sincere, offer a serious counter-witness to Catholic belief, which can only produce moral confusion in the community. Such a relationship cannot be accepted into the life of the parish without undermining the faith of the community, most notably the children."

Mia Trotz, an 18-year-old college student from Philadelphia who was selling ice water outside the cathedral, told Philly News the guidelines did not make sense.

"The whole part about being a good Catholic or Christian is helping people or being more accepting of people, but most of the time they're going against what they're telling you to do," she said of church leaders.

"I'm Catholic but I don't agree with everything they do or believe, so it's kind of hard to be Catholic sometimes."