In the letter published in the Daily Telegraph, the priests claim that same-sex marriage could even lead to Catholics being excluded from some professions, such as teaching.

The letter, signed by 1,054 priests as well as 13 bishops, abbots and other senior Catholic figures, raises fears that the simple acts of practising or speaking about their faith will be severely limited.

They go so far as to compare David Cameron's proposed changes to the meaning of marriage to those of Henry VIII, whose efforts to divorce Catherine of Aragon sparked centuries of upheaval between church and state.

Their fear is that Catholics who believe in the traditional meaning of marriage would effectively be excluded from some jobs – in the same way that Catholics were barred from many professions from the Reformation until the 19th century.

It said: "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."