The secretary-general of the Italian bishops' conference said 'unconventional couples' must not be discriminated against.
Bishop Nunzio Galantino said: "Couples in irregular matrimonial situations are also Christians, but they are sometimes looked upon with prejudice".
He told Italy's ANSA news service it's unfair to exclude some people from Holy Communion because of personal circumstances.
"[It] is an unjustified price to pay, in addition to de facto discrimination," he said.
It's not the first time he's spoken out. In May he urged other Church leaders to "listen without any taboo to the arguments in favour of married priests, the Eucharist for the divorced, and homosexuality."
Last year the Vatican sent a survey on issues from same-sex marriage to surrogacy to all priests before a meeting called by Pope Francis in October to discuss Church policy on family issues.