Above, Ian Harvey, from heroin and rough sleeping to charity volunteer, gardening enthusiast and Chelsea Flower Show winner.

The big society concept might be a touch nebulous – as its creator Philip Blond effectively admitted this week – but one transparent element is the fact that volunteers are its backbone.

The drive is a potentially all-inclusive one as the big society dream is of a volunteering renaissance that unites the young (nothing else paid on offer), the more mature (nothing else to do in well-heeled retirement) and the professional (nothing as good as a bit of CSR in the city to justify that fat salary and boost the CV).

But any official messages about big society bypass a huge swath of society; the homeless.

The vulnerable are excluded from the big society agenda and a potential volunteering resource remains untapped, as new research published this week by homelessness charity St Mungo’s argues. The organisation suggests that volunteering can help the homeless move from social exclusion to being active in their community.

Its figures show that only 14% of around 200 St Mungo’s clients and staff surveyed (84 of the 200 were clients) think homeless people are included in society. The report from St Mungo’s, Enough Room: is society big enough for homeless people?, has been released to coincide with the charity’s action week to raise awareness about the social exclusion of the homeless. According to the latest figures, 3,975 people were seen rough sleeping in 2010/11 on the streets of London – a rise of eight per cent from the previous year.

The charity says there’s a real wish among those it supports to give something back. Of the homeless clients surveyed, 70% wanted to volunteer to “give something back to their local community” or to “help other people.”

Investing time in supporting vulnerable people to volunteer can bring long-term benefits – stability, greater self-esteem and social integration and the chance to develop new skills.

I recently came across the Crown Centre in the deprived area of Stonehouse, Plymouth, for example. The centre supports vulnerable people through projects such as the Plymouth Foodbank, ensuring those in crisis do not go hungry. Every week, the centre relies on its 47 regular volunteers to run coffee and lunch clubs supporting 120 service users. Half the volunteers have health or dependency issues and are “supported volunteers”, needing more guidance and supervision than their peers donating time for free.

Back in London, St Mungo’s client turned volunteer Ian Harvey (scroll up to the video above), is the kind of volunteer we could have more of. Ian, a former rough sleeper and ex-heroin addict, has been supported by St Mungo’s to work with the charity’s community gardening scheme, Putting Down Roots. Ian has tuned his life around with specialist support and from involvement in the volunteering scheme; not so long ago he was self-harming and sleeping on the streets, now he’s the proud owner of a silver award from the Chelsea Flower Show and is looking forward to winning gold next time.

Roger is another St Mungo volunteer, a former drug-user who slept rough, he volunteers for the charity’s employment team and encourages clients to improve their basic computer literacy skills. He explains: “I realised that the key to me moving on with my life was training and qualifying. It also became very clear that I would get nowhere without knowing my way around a computer …Since November last year, I have been volunteering for St Mungos’ employment team and have been helping more clients get online with weekly drop in sessions and support with basic computing courses.”

Lorette, a volunteer peer advisor with St Mungo’s resettlement service, explains the strength of the ex-homeless supporting those who still need support: “I think the client feels they can relate to you more if you have been through what they have. You can swap stories and experiences, which I think enables them to open up to you more…Volunteering is great for your self esteem and confidence, especially if you have been out of work for a long time, there’s new skills to learn, great people to meet and a great feeling of self worth that you really are helping people and doing something really worthwhile.”

Yet so far the big society drive has largely failed to include or capture the attention of the vulnerable. As the St Mungo’s research demonstrates, the neediest in society neither feel part of the campaign nor understand what it stands for (although frankly they’re not alone in that latter complaint). A big society, but one that’s currently too small for the vulnerable.