The government is under pressure on police cuts and rightly so. But a civilised society requires more than this. Our neighbourhoods must be policed not just by uniformed officers, but also notions of pride and shame and responsibility to others. How we achieve that is the most difficult and the most important question in the wake of the riots.

Rightly, a debate is opening up on the family. To have children is a moral choice. To be there for them is a civic duty. None of us are perfect, but too many parents in Britain are either absent or not doing their job properly. Successive governments have backed off the issue of parenting, fearing cries of the "nanny state", but we can no longer rely on Mumsnet and Supernanny to do the job for us. Half of all parents, across of social backgrounds, express an interest in attending parenting classes. They should have access to them. Likewise, if we expect people to work long hours for low pay, can we really be surprised when they are not around to supervise their children? Society has responsibilities to parents as well as visa versa.

Families cannot do it alone, however. We must also come to terms with some important social changes. We are less likely to know our neighbours, or to live and work in the same area. There are fewer community figures around, from the bus conductor, to the park warden who might intervene when children cross the line. As strangers, the rest of us hesitate to get involved; seven in ten of us say we would now walk on by if we saw a group of children vandalising a bus stop - more than anywhere else in Europe. There are no longer the surrogate parents in neighbourhoods to reinforce messages that come from within the home.

Instead of these forces for civility, modern Britain has a popular culture which can pull children in another direction. Children spend twice as much time in front of a TV or computer screen as they do in the classroom. This facilitates an online peer-to-peer culture, where adults are almost entirely absent. It contributes to a Grand Theft Auto culture, in which films, video games and popular music glamorise violence. And it helps reproduce a shallow consumer culture, with its obsession with the brands behind those smashed windows in JD Sports and Carphone Warehouse.

In the face of these changes our civic institutions matter more than ever. Robert Baden-Powell, the founder of the Scouts, described its mission as to foster a "spirit of self-negation, self-discipline, sense of humour, responsibility, helpfulness to others, loyalty and patriotism" in young people. Modern Britain needs more of this, not less - civic institutions on scale of the Scouts, the Girl Guides or the Boys' Brigade, which ground young in people the habits of citizenship.

For me this makes the case for a national civic service unanswerable. Those involved should be enrolled in schemes that involve visiting the elderly, helping out in schools, mentoring younger children and renovating public spaces. The idea has a heritage in the Labour Party, dating back to the social justice commission, established by John Smith as leader. In government when I raised this idea it was always knocked back. "Too controversial". "Too complicated". "Too expensive". There should not be such equivocation now. The same reservations now risk undermining the coalition's plans in this area.

The government has committed itself to a civic service in principle, but its plans look more like a glorified gap year scheme for the wealthy than a sustained programme that will reach everyone. The programme is voluntary. It will last just seven weeks. Those taking part in it will have to fund themselves, including a charge to take part. Ministers should ask themselves how many of the rioters, looters and those who were tempted to join them are really likely to sign up.

Now is not the time for half measures. A British civic service should be compulsory. It should last at least six months, allowing for a truly transformative experience. Each participant should be paid the minimum wage to help them get by. It should give those taking part a taste of people and places very different from what they are used to. It should draw in the private and the voluntary sector to help provide structured and supervised projects for our young people to take part in.

There is nervousness in Whitehall around compulsion, but we already support compulsory education until eighteen. Why is six months more so troubling?

A YouGov poll in 2009 found that two thirds of adults support the idea of a compulsory civic service. The Treasury may baulk at the cost, but last week revealed the costs of inaction. With youth unemployment at record highs we already pay many to sit at home. Corporate sponsorship should be encouraged from those who want to play their part.

I have seen the value of these programmes myself. I have visited the City Year scheme in New York, which brings together young people of all backgrounds for a year of full time service. It is a far cry from the parallel lives in this country by those who rioted and those who took part in the clean up. People of different ages, backgrounds and races mix together, doing something positive for the communities they work in. Those from wealthier backgrounds help out in tough schools and begin to understand more about life on the other side of the tracks. The kids from those schools are encouraged to believe they could be mentoring others one day.

City Year commands cross party support in the States. Pictures of JFK adorn the walls of the organisation's Manhattan headquarters, while the organisation counts Mayor Bloomberg as one of its biggest advocates. In Britain proposals to emulate it on a national scale are always met with the same answer: "not now". After the looting, rioting and chaos last week we should reverse the question: if not now, when?

David Lammy is the MP for Tottenham