One of the most exciting, widely supported and quickly growing social justice campaigns is about to be celebrated this week. And it's an idea which didn't spring from politicians, think tanks or focus groups. It came from churches, where ordinary Christians teamed up with their friends of other faiths and none to bring major change.

The Living Wage campaign began in churches and other civil society institutions 15 years ago. But the idea itself is much older, and comes from Christian theology. The modern idea of the Living Wage was first raised in a Papal encyclical in 1891. Since then it has become a core building block of Catholic Social Teaching. Of course, it goes back even further back than that. In Deuteronomy 24 we read, "You shall not oppress a hired servant who is poor and needy, whether he is one of your brothers or one of the sojourners who are in your land within your towns. You shall give him his wages on the same day, before the sun sets (for he is poor and counts on it), lest he cry against you to the Lord, and you be guilty of sin."

The New Testament too contains plenty of references to making sure workers get what they deserve. "Now to the one who works, his wages are not counted as a gift but as his due," Paul says in Romans 4. In this context we can understand Jesus' command to his disciples: "You yourselves give them something to eat!" (Mark 6:37). It means working to eliminate the structural causes of poverty and to promote the integral development of the poor, as well as small daily acts of solidarity in meeting the real needs we encounter.

So what is it?

The Living Wage is currently £7.85 an hour outside of London and £9.15 an hour in London. It is independently calculated on what it actually costs to live. It allows for a family to have a one week UK-based holiday per year, for example, but some things like smart phones are not included.

This week, the new Living Wage figures will be announced and more than 1,500 employers who are accredited as Living Wage employers will respond accordingly and adjust their employees' pay.

The Most Revd John Sentamu, Archbishop of York, was the Chair of the Living Wage Commission. He said, "I've seen first hand the difference that the Living Wage has made in the lives of employees and their families. We must take seriously the words of Jesus Christ: 'The worker deserves his wages.' He treated people with respect, and we must do the same. Employers have also greatly benefited as loyalty from employees has resulted from paying the Living Wage."

Should it be compulsory?

Some would like to see the Living Wage become compulsory (indeed, the Chancellor George Osborne has re-branded the Minimum Wage as the 'National Living Wage' although it falls short of what it actually costs to live). The problem is that some small and medium sized businesses struggle to pay the Living Wage.

This means it needs to be voluntary but there should be no reason for large companies and state employers not to pay it. Indeed, research by KPMG suggests that paying a Living Wage is not only good for staff and their families – it is good for business as well. In addition, by paying people properly, the welfare bill is reduced, as fewer people need to rely on Tax Credits and other government support schemes to top up their poverty wages.

Is it going to happen widely?

Already over £200 million extra has gone into the pockets of low-paid employees as a result of the Living Wage. When the Living Wage campaign began we were told it would be impossible to introduce. But now, major high street retailers such as Lidl and Aldi have joined huge companies such as GSK, Aviva and Nationwide and major employers like the Mayor Of London. It is a campaign that has momentum – and churches across the UK are backing it this week (you can see some tips on how to join them here).

Shouldn't we be focussing more on 'spiritual things?'

We know that God cares about the whole of our lives. He cares when a parent has to work two or even three jobs because they don't get paid enough. He cares about the impact this has on family life. He cares about the lack of dignity given to people who work for poverty wages. He cares about those who do some of the most important jobs in our society – such as cleaning our hospitals and caring for our older relatives. God's care suggests these people should be given a just wage for their work.

The success of the Living Wage campaign is a good news story for the Church to tell. We have been at the heart of a movement which is benefiting many people and changing their lives for the better. We're doing this because we believe in the God-given dignity of each person. And with churches so prominent in this campaign, it shows our Gospel witness is credible – we have a God who cares deeply about every aspect of our lives and we're quite literally putting our money where our mouth is to show it.