In a letter to The Daily Telegraph, 1,054 priests -- along with 13 bishops, abbots and other senior Catholic figures -- alleged that allowing same-sex couples to marry could limit the clergy's freedom to practice and speak about faith.
"After centuries of persecution, Catholics have, in recent times, been able to be members of the professions and participate fully in the life of this country," the letter said. "Legislation for same sex marriage, should it be enacted, will have many legal consequences, severely restricting the ability of Catholics to teach the truth about marriage in their schools, charitable institutions or places of worship.
"It is meaningless to argue that Catholics and others may still teach their beliefs about marriage in schools and other arenas if they are also expected to uphold the opposite view at the same time," the priests wrote.
The priests called on members of Parliament to "not to be afraid to reject this legislation now that its consequences are more clear."