Greater protection for the marriage beliefs of Christians has gained the overwhelming support of MPs.
MPs voted 86 to 31 in favour of amending the Equality Act to protect "conscientious beliefs on marriage".
The proposal was contained within a Ten Minute Rule Bill moved by Conservative MP Edward Leigh.
The vote comes a week before the second reading of the Government's Same-Sex Marriage Bill.
Mr Leigh said that the bill as it currently stands does not offer adequate protection to Christians and others who hold to a traditional understanding of marriage.
He wants the bill changed to ensure that they are not penalised for their views.
MPs were reminded of the recent case involving Adrian Smith, who was demoted and received a pay cut for saying on his personal Facebook page that gay marriage in churches was "an equality too far".
Mr Leigh warned that the redefinition of marriage may lead to thousands more people being disciplined by their employers, sacked or treated as outcasts.
Efforts to protect Christians follow a warning from leading human rights barrister Aidan O'Neill that the Government's plans will have serious consequences for those working in the public sector, using public facilities like community centres, or wishing to receive public funding.
Earlier in the month, Christians Lillian Ladele, a registrar, and Gary McFarlane, a relationships counsellor, lost their conscientious objection cases at the European Court of Human Rights.
Speaking after the vote, Mr Leigh commented: "Army and NHS chaplains who preach in favour of traditional marriage in their own churches on Sunday could find themselves in trouble for it at work on Monday.
"Tens of thousands of teachers are at risk of disciplinary action for expressing traditional views on marriage.
"Although my bill to help these people will not become law, by voting for it today the House of Commons has expressed concern about this important issue.
"We must now make sure at the very least that the Government's same-sex marriage bill is amended along the lines we have proposed."
The second reading of Mr Leigh's Bill is scheduled to take place on 1 March.
Andrea Minichiello Williams, Director of the Christian Legal Centre, said the redefinition of marriage was "creating a climate that will lead to the exclusion of Christians from serving society".
"The debate on the Government's Same-Sex Marriage Bill next week will highlight this. Many people – MPs and members of the public – are deeply concerned.
"The Judgment from the ECHR two weeks ago shows that people with Christian views on marriage are already being excluded from certain areas of public service.
"The British Government has shown itself to be ignorant about the nature of Christian faith. As the ECHR reminded them, views on marriage are a manifestation of Christian faith.
"Christians won't be duped by the Government, nor will others who believe that marriage should remain as being between one man and one woman."
