Parliament has decided that marriage should be something other than what it has been throughout history and different from its natural and biblical meaning.

Now it is the task of the Church to model marriage to a society that has forgotten what it is. This contentious social change may well grieve God's heart, but He is certainly not fazed by it, and nor should we be. In all challenges there are opportunities, and in the light of pressures that Christians and others will no doubt face in coming years, this new legal fiction offers a chance to model and teach what marriage really is.

The state's new view of marriage means it is no longer a lifelong union between a man and a woman for the procreation of children and the foundation of family life. Now it has been changed and effectively privatised to privilege adult choice. The changes have stripped husband and wife of their obvious meaning and marginalised adultery and consummation. Marriage is now a fluid, gender-neutral institution defined by consumer demands and political expediency and it is likely that pressure for further changes to it will follow. As the Archbishop of Canterbury observed: "Marriage is abolished, redefined and recreated, being different and unequal for different categories."

Importantly, this change was not in any party manifesto, it was not in the coalition agreement, and despite the fact civil partnerships already confer all the rights and privileges of marriage, the state is now enforcing a new social orthodoxy. While some of the changes may be imperceptible at first there are profound implications for all of society and Christians in particular. In politics, education, welfare, health and employment same-sex marriage will be presented as normal and those many groups and individuals who hold to a different view will therefore need legal protections.

The Evangelical Alliance campaigned extensively alongside many others to preserve the traditional definition of marriage and continues to be committed to advocating for religious freedom and keeping the Church informed. The Alliance will continue to work hard to ensure protections are secured and maintained for people such as teachers, pastors and doctors in the public sphere, as well as ordinary people in everyday life who express the belief that marriage can only be between a man and a woman. This will include working with the Equality and Human Rights Commission who are tasked with drawing up appropriate public guidance to the new legislation. It will also involve as a core member of the Coalition for Marriage working to develop partnerships across Europe and the globe to promote and protect traditional marriage.

Evangelical Alliance director of advocacy, Dr Dave Landrum, said: "On this highly contentious issue the government failed to properly consult, ignored overwhelming opposition, and were determined to avoid public debate. They have failed to think about what marriage actually is, or the impact on children, and they have fast-tracked the legislation to bypass democracy. Votes were informally whipped, and the government persistently refused to allow amendments. Protections that are essential and would normally be expected in a situation like this were brushed aside in their haste to get this onto the statute books. They clearly hope it will fade as an issue before the next general election.

"For Christians it is important to distinguish between fact and fiction: although the law has changed, real marriage is and will always be exclusively a lifelong union between a man and woman. We can acknowledge the fact the legal definition has changed but we should also understand that we do not need to approve of the legal fiction created.

"In the knowledge that God is not fazed by this, we should have confidence to speak and teach the truth with grace and love. And as we help each other to sustain marriage as a covenant before God through which two become one, I hope we will be taking valuable opportunities to witness to the good news of Jesus Christ."

The Evangelical Alliance will shortly be circulating a briefing for churches with more detailed information about the likely impact of the redefinition of marriage.