There is a group of people who are chronically excluded from housing, work, relationships and the kinds of activity most people aspire to in 21st century Britain. They exhibit the most complex problems but they can be the most excluded from the very help they need.

Many agencies find these people difficult; some agencies may be pleased not to find them at all. But, wherever they land "when the music stops", agencies find them expensive to support.

For some people, the problem is that they do not get help when they need it. They fall outside of every service. The Sainsbury Centre's own recent work has shown that many people have a whole set of needs, none of which is regarded as severe in its own right: they fall below every agency's "threshold" for a service.

We have interviewed women with depression or anxiety and drug or drink problems who commit minor offences and, in several cases, have nowhere to live. Short prison sentences and a lack of family and local connections can almost guarantee they will be back with the police and in the courts pretty soon. Surely this option really is one of last resort.

Others are recognised as needing healthcare, but there is confusion and a lack of clarity about what is being done and by whom. In 2007, crime reduction charity Nacro found that some of its clients with severe mental health problems had seen as many as 23 professionals from seven different agencies; and in their world there are no prizes for high scores.

These excluded people with mental health problems need a degree in inter-agency working if they are going to get their needs met.

Bottom of the heap

Some people with "chaotic lifestyles" do not appear in the offender statistics. But they are constantly batted between statutory agencies dealing with homelessness, addictions and, probably in the future, access to welfare benefits. With a range of mental health and developmental disorders, difficulty in managing their lives, few friends and little money, they are likely to fall to the bottom of the heap and find themselves written off.

The social exclusion task force has acted nationally to set public service agreement targets focusing on employment and settled accommodation for excluded adults with mental health problems. The programme for adults facing chronic exclusion is following pilots that test ways of tackling problems for this group of people. This creates a framework and a set of expectations from government. However, it is not clear where the spur for action by health will come.

The Darzi review recognises the role of the NHS in partnerships for well-being and prevention. But, in truth, people experiencing chronic exclusion will not be at the centre of this agenda unless local partners really drill down into their shared local knowledge about the most excluded and until local agencies are prepared to commission for those who live chaotic lifestyles.

The most excluded need support, they cost money and they often end up in the wrong part of the system. The pay-off for the NHS, including mental health, from recognising who those people are and then focusing on innovative solutions, could be to make a significant contribution to tackling the most serious inequalities in their communities.