The Lutheran bishop who received Communion from a Catholic priest in the Vatican ought not to have been offered it and should have refused, according to a spokesman for the Catholic diocese of Helsinki.

The Lutherans from Finland, led by Bishop Samuel Salmi of Oulu, were part of a delegation in Rome for the Week of Prayer for Christian Unity. They indicated by crossing their right arms over their chests that they should not be offered the sacrament at Mass in the Basilica, but the priests went ahead and gave it to them regardless.

Bishop Salmi said the Catholic priests had known who the Lutherans were, so they had not been invited to partake by mistake.

"Catholics shared the Eucharist. I also got to be part of it," he said. For Bishop Salmi, the move was part of a greater openness toward intercommunion, signalled by Pope Francis' advice to a Lutheran woman married to a Roman Catholic that she should "talk to the Lord" about whether to join him at Mass.

However, the diocese of Helsinki has issued a robust denial of his interpretation of the event and said that Catholic teaching had not changed.

"Only members of the Catholic Church in the state of grace may receive the Catholic sacrament of the Eucharist, or Holy Communion," according to Marko Tervaportti, director of the diocese's Catholic Information Centre.

He said that the priest may not have known the identity of the Lutherans, as crossing the right arm to the left shoulder as a sign of seeking a blessing rather than Communion was not a universal practice. He added that "if communion is offered, it is because of the ignorance of the minister of the Eucharist and it can still be politely refused".

According to Tervaportti, "The doctrine and practice of the Catholic Church with regard for whom it is possible to receive Holy Communion has not changed in recent years and decades. If it does change, it will not happen 'in the field', but through an alteration of Church law and additions to teachings regarding the sacraments of the Catholic Church."

He urged the necessity of theological engagement, saying that attempting to create communion "on one's own authority" hindered "the true efforts of the churches to draw closer".

While Lutherans and Catholics have seen a significant rapprochement during the last few years, traditionalist Catholics have been angered by what they see as too many concessions to the Lutheran tradition.

Pope Francis' words to the Lutheran woman who asked him about taking Communion in a Catholic church have been explained by theologians as an expression of sympathy rather than of approval.