In one of the biggest joint letters of its type ever written, they raise fears that their freedom to practise and speak about their faith will be “severely” limited and dismiss Government reassurances as "meaningless".
They even liken David Cameron’s moves to redefine marriage to those of Henry VIII, whose efforts to secure a divorce from Katherine of Aragon triggered centuries of bloody upheaval between church and state.
They claim that, taken in combination with equalities laws and other legal restraints, the Coalition's plans will prevent Catholics and other Christians who work in schools, charities and other public bodies speaking freely about their beliefs on the meaning of marriage.
Even the freedom to speak from the pulpit could be under threat, they claim.
And they fear that Christians who believe in the traditional meaning of marriage would effectively be excluded from some jobs – just as Catholics were barred from many professions from the Reformation until the 19th Century.
This is not an unjustified fear, nor is it scaremongering. It's happened before.
Rev Dr Andrew Pinsent, a leading Oxford University theologian, who also signed the letter, said: “We are very sensitive to this historically because of course the reformation started in England as a matter of marriage.
“Henry VIII could have been forgiven for his adultery but he didn’t want to do that, he wanted to control marriage and redefine what was a marriage and wasn’t.
“Because the Church would not concede that point, that launched three centuries of great upheaval in English society, and from the Catholic point of view life was very difficult."
A number of old English houses have "priest holes", a hole in the floor where a priest could be hidden from agents of the State. Being a Catholic priest during the years that the "priest holes" were in operation generally made for a very short life span.
All the hatred of the enemy is generally most aggressively directed at priests, for they make Christ physically present on earth. This letter shows that even full on liberal Catholic priests, according to Damian Thompson who recognised a number of the names, realise what they are facing and so will be quiet no longer.
It's not just Catholics who will be in the firing line, either, it's any person who holds the politically incorrect view that marriage can only be between a man and a woman.
Related links: Gay marriage could signal return to ‘centuries of persecution’, - say 1,000 Catholic priests ~ The Telegraph
Gay marriage: after today's letter in the Telegraph, the Catholic Church really is at war with the Government ~ Damian Thompson, The Telegraph
Once marriage is redefined, everyone will be at risk ~ Bob McCoskrie's Blog