Portugal's Cardinal Jose Policarpo has warned young women in the predominantly Catholic nation against marrying Muslims.
"The advice that I give to young Portuguese girls is – be careful with relationships, think twice about marrying Muslims," the patriarch of Lisbon said.
"It is getting into a pile of troubles, that not even Allah knows where would end."
Policarpo made the statement at a gathering on Tuesday evening in a well-known casino that organises meetings of public figures with paying guests. His comments were repeated on several television stations on Wednesday.
There are about 40,000 Muslims in Portugal, which like neighbouring Spain was once ruled by Muslims from north Africa, where many Muslim immigrants come from.
The country's biggest Islamic organisation said it was upset by the comments.
"We were in a way hurt by the choice of words by the patriarch of Lisbon about our community and about the dialogue that we have sought with all religious denominations, and especially with the Christian religions," the Islamic Community of Lisbon said in a statement.
The Vatican discourages Catholic women from marrying Muslims and Policarpo echoed that position in blunt terms.
"I know that if a young European of Christian background marries a Muslim, as soon as they go to his country, they'll be subject to the regime of Muslim women," Policarpo said. "Just imagine it."
Policarpo, a leading cardinal who was tipped as a contender in the 2005 conclave that elected Pope Benedict, also said dialogue with Muslims was not easy in Portugal.
"It is only possible to dialogue with those who want to have dialogue, for example with our Muslim brothers dialogue is very difficult," he said.