IMAGINE, five years ago, that you were asked: "What would happen in Britain if hundreds of thousands of people were no longer able to afford enough food?" If it was me, I think I would have guessed that local councils would have organised something.

What has actually happened, however, is that the churches have stepped up to the plate. The Trussell Trust co-ordinates a fast-growing network, now numbering more than 400, of charitable foodbanks, all of which are church-based.

Three more open every week. They draw on charitable donations of food, and on large-scale volunteer effort. Between them, they provided food for more than half a million households between April - when the bedroom tax, and other benefit cuts kicked in - and December last year.

Most people think the churches in Britain are experiencing a slow but inexorable decline into irrelevance. The truth about Britain in 2014, however, is rather different. Only the churches have had the capacity to address a sudden crisis of food poverty.

And it is not just foodbanks. Debt advice, street pastors, helping jobless people into work, tackling homelessness, and international development: in all these areas - and many others - the churches are making a remarkable social impact.

We are seeing a new wave of church-based social activism. It is not just activism undertaken by people with a background in Christianity. Rather, it has the activity of worship right at its heart. This is what gives it energy and commitment.

THE number of people on the electoral registers of churches in the diocese of London fell sharply in the 20 years from 1972. But in 1992 the trend reversed. In the next 20 years, numbers climbed steeply - and, by 2012, they were back at 1972 levels, and still rising.

Immigration has been a big factor, and no doubt Alpha courses have played a part. But that numerical evidence - as well as reports of what is happening in communities across the country - suggest that the old assumption of declining social impact needs to be junked.

IN THE part of London I represent, London Citizens - a coalition of churches, mosques, schools, trade unions, and community organisations - has had a huge impact. It has enlisted young people to political campaigning far more effectively than the political parties did. It successfully recruited formerly unemployed people, many reached through their church or mosque, to work at the London 2012 Olympic and Paralympic Games. And it developed the idea of the living wage - an idea now taken up by politicians in every party.

Last year, I chaired the advisory committee for a study by the think tank Demos. Its conclusions were published last September, in The Faith Collection: Exploring the role of faith in British society and politics.

Drawing on data from the European Values Survey, it showed that people who said that they belonged to a religious organisation were far more likely to volunteer than people who did not.

In fact, the survey found that the one-in-eight of British respondents who said that they belonged to a religious organisation accounted for more volunteers with trade unions, in local community action, on women's issues, and on human rights and development than the seven-in-eight who did not. And the report points out that the political implications are far-reaching.

I chair the All-Party Parliamentary Group on Faith and Society. We have taken evidence from a wide range of faith-based organisations. Many of them report reluctance on the part of local authorities to commission public services from organisations such as theirs. Inour view, this reluctance is misplaced.

CONSEQUENTLY, we have drawn up a draft "covenant", comprising commitments to be signed up to by both local authorities and by faith-based organisations that are seeking local-authority contracts.

We hope that it will help to address the current reluctance. Local authorities recognise that austerity will require radical new ways of meeting needs in their communities. A few forward-thinking councils see partnership with faith groups as a promising option. We are discussing pilots of our covenant with a couple of city councils.

Of course, by some yardsticks, the social impact of the Church is much less than in the past. Its impact on public policy is slight - church opposition to the Prime Minister's Marriage (Same-Sex Couples) Bill appeared to have minimal effect on the public debate. Many people have no idea what happens inside churches - and no inclination to find out, either.

But popular respect for the Church, however ill-informed, has been maintained. In disadvantaged neighbourhoods, where many institutions have pulled out, the Church is sometimes the only one left. In those situations, it represents hope.

In previous centuries, waves of church-based social activism have had profound and lasting effects on Britain. They have delivered social progress. They have forged new forms of social organisation, and enduring institutions. It is too early to judge the long-term effects of this current wave, but the scale of it suggests that the effect will be substantial.

Stephen Timms is the MP for East Ham, and Shadow Minister for Employment.