They are calling on MPs to make urgent amendments to the Government’s same-sex marriage bill, which will be debated on Monday, to protect Christians and others with traditional views from being punished in the workplace for their beliefs.
Otherwise, it could have a “chilling effect” on young people’s career choices, deterring many from going into public service or charities in case they are branded homophobic for speaking about their beliefs, they fear.
The call comes in a letter to The Daily Telegraph signed by an informal grouping of Christian leaders ranging from the second most senior Roman Catholic cleric in England and Wales to Anglican vicars and independent evangelical pastors.
It follows an unprecedented letter from more than 500 imams accusing the Government of attacking “the cornerstone of family life”.
Young people, will be forced to “choose between their conscience and their career”, the church leaders write.
Unless it is amended, the bill will “cause pain for many, without tackling prejudice against the few”, they add.
The call echoes concerns raised by the Church of England in a briefing to MPs last week.
It follows a series of cases in which people who voiced traditional beliefs to colleagues or asked to opt out of activities on what they saw as grounds of conscience were deemed to be breaching equalities rules preventing discrimination against gay people.
Adrian Smith, a housing trust worker from Trafford, Greater Manchester, was demoted from his managerial post after mentioning in a Facebook discussion that he thought churches should not stage gay weddings. He later won a High Court challenge but has not been reinstated.
The church leaders say that the Smith case shows there is a need for explicit protections for traditionalists working in the public sector to be written into law.
If not, they say many young people will simply choose other career paths, depriving the country of major pool of talent.
The letter signed by the Roman Catholic Archbishop of Southwark, the Most Rev Peter Smith, and the directors of “Co-Mission” an Anglican-led group of newly formed congregations and the Fellowship of Independent Evangelical Churches.
Other clerics who have signed include the Rev Vaughan Roberts, a prominent Oxford evangelical who recently disclosed that he “struggles with unwanted same-sex attraction”.
Together the signatories calculate that their congregations include 150,000 people of whom at least a third are young people.
“These young people, from teenagers to 30-year olds, will suffer discrimination, and will face new risks to their career and future,” they write.
“If the Bill passes into law without much clearer protections for freedom of speech and freedom of belief, teachers, and public sector workers will have to choose between their conscience and their career; many will be deterred from a public service career and from charity involvement.”
They say that the so-called “public sector equality duty” which imposes a legal duty on public bodies to promote equal rights for gay people and eliminate discrimination is being used to prevent Christians and others speaking about their beliefs.
A clause of the 1996 Education Act also requires schools to teach children the nature and meaning” of marriage – something the church leaders say could force Christians to go against their conscience once the bill is law.
The Rev Charlie Skrine, of St Helen's, Bishopsgate, in London, said: "The young people I minister to share none of the homophobia that may have been present in earlier generations, but many of them have deep convictions of conscience about marriage that come from their own reading of the Bible.
“These young people have real reasons to worry about their future if the bill is passed without significant amendments to protect their freedom of speech and freedom of belief.
“The bill seeks to protect the consciences of vicars, but many public professions will be weakened if these young people are deterred from entering them for fear of legal action and discrimination if they express a biblical view of marriage.”
The Church of England briefing note argues that a short amendment to the Equality Act could be made to make clear that expressing a traditional view marriage should not be viewed as discrimination.