Jonny Scott is sipping coffee at the kitchen table of another stranger. Though they met just this Tuesday afternoon, Matthew Morgan is chatting freely about his wife and kids, about his decision to give up his job to do a history of art PhD and about the activities of All Saints, Fulham, the neighbourhood church.

All very pleasant and prosaic, perhaps, but Jonny is at work. It’s a job he’s been doing for precisely a year, one that could hardly be more voguish among the great and the good: he is a community organiser for London Citizens.

It is an organisation that represents over 150 groups – churches, union branches and student unions – in the capital, covering perhaps 300,000 members. The groups pay an annual fee of between £1,600 and £1,800 in return for the help of people like Jonny, and for London Citizens’ growing national clout. James Purnell famously stood down as an MP at the election to become a community organiser. Earlier this year, he attended a five-day training course run by London Citizens in Hemel Hempstead.

Jonny’s bread and butter are his ‘one-to-one’ meetings with people from member organisations, finding out what they want and ‘identifying leadership and talent’. ‘Leaders’ such as Purnell are then trained in London Citizens’ methods of deliberation, negotiation and ‘broad-based self-interest’, the idea that by working together they can achieve their goals.

‘Saul Alinksy’s iron rule,’ says Jonny, referring to the 1930s Chicago radical usually cited as godfather of modern community organising, ‘was don’t do for others what they can do for themselves.’ Matthew’s is one of hundreds of one-to-ones he’s done since starting the job: ‘I’ve spoken to people whose lives are crippled by debt, or on exploitative wages, the victims of violence, as well as archbishops and politicians.’

Many of the different groups’ concerns are ultra-local but London Citizens has a number of central campaigns too: a London ‘living wage’ of £7.60; an amnesty for working migrants in London; a ban on extortionate doorstep lending; a tax on the nationalised banks to fund fairer local lenders; ending the incarceration of children at immigration detention centres; and, inevitably, more affordable housing.

These were all policies that, a few years ago, were dismissed by mainstream opinion as too radical, too costly, too liberal. Why, then, are politicians, the media and business starting to sit up and take notice? And with the combined membership of the three main political parties at a historical low – perhaps under 500,000 – are they increasingly irrelevant compared to grassroots organisations such as London Citizens?

Since Purnell’s announcement that he is to follow in the footsteps of Barack Obama into community organising, London Citizens has hardly been out of the news. Gordon Brown, David Cameron and Nick Clegg each addressed the Citizens UK conference in the runup to the general election. Ken Livingstone agreed to pay the London living wage to all workers in City Hall before losing the London mayoralty in 2008. Boris Johnson vocally carried this on; so have companies like Barclays. And the current Labour leadership election has seen both Miliband brothers, and Ed Balls, call for the party machine to learn from community organising. Ed Miliband has adopted a national living wage rate of £7.14 as a central plank of his campaign.

They are acutely aware that the success of organisations like London Citizens, and campaigns like Make Poverty History, comes at a time when people are shunning mainstream politics as a means of achieving their goals. David Babbs, director of online campaigning organisation, 38 Degrees, says: ‘We launched at the end of May 2009, and at the last count had 67,000 people involved.’

Babbs adds that people have been attracted to 38 Degrees’ campaigns because they are responsive. One topical example is their campaign to ‘Stop the BBC’s enemies getting their way’, in the face of proposed cuts and attacks from the Murdoch empire. ‘We asked our members whether this was something they wanted us to campaign on, challenging this view, and 90 per cent said yes.’

People are attracted to this ‘flexible’ and ‘opt-in’ approach, he says: ‘They are looking for a sense of agency, as a way of making a difference. Fewer people are looking to political parties to do this. Many of our members are not associated with political parties: it has become a hated label for some people.’

So, is there any reason why grassroots and online organising could not replace political parties as people’s main mode of political expression? ‘They could if political parties allow them to,’ says Graeme Cooke, a researcher at Demos, though no democracy is entirely without political parties. Cooke is the co-author with Purnell of the Open Left project, asking whether Labour can harness some of the campaigning energy currently going on outside the party.

They argue that Labour can do this if it revisits its traditions of unionism, workers’ co-operatives and friendly societies of the late 19th and early 20th centuries. So does Dr Maurice Glasman, British community organising’s main intellectual. Glasman is deeply involved in London Citizens, despite being a Labour member. Following a London Citizens conference in East London, he says: ‘I am deeply Labour. I got involved with London Citizens because the Labour party didn’t exist as a local organisation committed to the common good.’

Both main parties are attempting to claim this tradition as their own. Scribbling away at the East London conference is Steve Hilton, Cameron’s director of strategy. Dr Glasman has invited the Harvard political philosopher Michael Sandel to lend some intellectual ballast to London Citizens. The political thinker Phillip Blond, self-proclaimed ‘Red Tory’, argued in Prospect magazine in February 2009 that there is a tradition of ‘communitarian civic Conservatism’ which stretches back to Edmund Burke and is suspicious of both the market and the state. Blond is close to both Cameron and Hilton.

Similarly, last year Dr Glasman launched a project entitled ‘Blue Labour’. ‘I have always seen myself as on the right of the party, as I believe in place, faith and family, though I am not particularly religious myself.’

He says in his speech to London Citizens that, ‘while the state and the market are both necessary and important aspects of a good society, left to the themselves they eliminate society entirely’.

Dr Glasman is scandalised that Labour could have ever allowed the Tories to try and lay claim to movements such as the co-op. ‘The fact we have allowed the Conservatives to have any credibility to claim mutuals as their own is an indication of how dire and statist we have become; taking responsibility for each other is the Labour creed.’

London Citizens and 38 Degrees are keen to stress their independence from political parties. But we shouldn’t necessarily group them together, either. Glasman is suspicious of campaigns that exist only online.

‘The internet is not going to build relationships. That was the mistake everyone made here about the Obama campaign. He never did politics through the internet, he did it through face-to-face local campaigning.’

Back in Matthew’s kitchen, he and Jonny are staring out of the window: ‘The garden is the next project.’ Would they be having this conversation if Jonny was wearing a red, blue or gold rosette? Probably not. ‘It has to be apolitical,’ says Matthew. ‘The church could never be so closely involved with a political party.’

This shows why organisations such as London Citizens will never fully replace political parties: they serve different, but overlapping purposes. There is no democracy in the world without political parties. But a party does not get access to the kitchens of people like Matthew for good reasons. Community groups should be open to the whole community, regardless of political creed. But it’s clear Labour could learn something about listening from these grassroots networks.