It was in July 2013 that 'Welby's War On Wonga' first hit the headlines. Two years on, an extraordinary amount has been achieved. By working with the wider community, the Church has helped secure the first cap on interest rates for over a century. Wonga's lending practices and its advertising are now undergoing fundamental changes. At local level, parishes are supporting credit unions and other new forms of community finance, as well as offering advice and support to those already in debt.

A similar story can be told on the issue of low pay. The growth of the Living Wage – another product of churches organising with their neighbours for justice – has played a vital role in the battle against in-work poverty. Over £200m has been won for working people through the Living Wage campaign.

These hard-won victories should be celebrated, but they are increasingly threatened by the rise in housing costs. People are not protected from poverty simply by earning a decent wage and having access to responsible credit. There needs to be housing available at an affordable level.

As General Synod meets in York, a new report shows how we can meet this challenge. Our Common Heritage urges churches to follow in the footsteps of Christian leaders such as Octavia Hill and Fr Basil Jellicoe, who founded housing associations in the late 19th and early 20th centuries.

The report celebrates some of the new partnerships local churches are developing with housing associations, which are not-for-profit organisations. It argues that the wider Church needs to learn from their good practice. In some cases, as congregations redevelop their buildings, they can release land for affordable homes. But that is only one of many ways local congregations can get alongside housing associations. As with the credit union movement, churches can provide volunteer support and be involved in joint campaigns for policies that support those in greatest need. They can also build relationships with tenants – in some cases, through formal chaplaincy arrangements with housing associations.

Of course, the churches' work with housing associations will not generate anything like the number of affordable homes that Britain needs. That is why the report argues that churches need to press for action by local and national government – not least through the Citizens UK alliance, which initiated both the campaigns for a Living Wage and a cap on interest rates. But churches cannot campaign in this way unless their actions embody their preaching. The churches' credibility in calling for a Living Wage has been related to their willingness to pay it. Likewise, the campaign for a cap on interest rates on payday loans has been greatly enhanced by the work local churches are doing to promote credit unions and to support those already trapped in debt. By supporting housing associations, churches can earn the credibility to campaign for the affordable homes that are so urgently needed.

The successes of the Living Wage Campaign and the 'war on Wonga' teach us something else. They demonstrate that numerical growth and social action need not be competing priorities. They can go together.

As Bishop Paul Bayes puts it: "The growth of the church is important, because we believe in a loving God who wants more people to know him and to work with him in the world. We want the church to grow, not just to make a bigger church, but to make a bigger difference in our lives and the life of our communities."

Growing churches have been at the heart of the campaigns for a Living Wage and a cap on payday lending. These churches are using numerical growth to make a "bigger difference" – and their commitment to the common good has been a powerful witness to the gospel. This in turn has been a catalyst to further growth. Far from pulling in opposite directions, numerical growth and social action have proved to be mutually reinforcing.

In the struggle for social justice, it is impossible to rest on past successes. It is good to celebrate the growth of the Living Wage and the cap on interest rates on payday loans. But unless we build on these achievements, the rising cost of housing will undermine their impact. If we want to make a "bigger difference" to poverty in Britain, we need affordable housing as well as affordable, ethical lending – a "Living Rent" as well as a Living Wage.

Canon Dr Angus Ritchie is Director of the Centre for Theology & Community, which published Our Common Heritage in partnership with Housing Justice. Find out more at theology-centre.org, which also has details of the Synod launch event tomorrow (Saturday).