"Australian cities are not planned to achieve social goals. They are organised so the poorest people … live in the outer suburbs, where public transport is also the poorest."

It's hard being green and lean - Environment - smh.com.au

Affordability is not the only barrier to cleaner forms of transport. Access to public transport is also a problem.

"If you live in the outer suburbs of Melbourne, about 90 per cent of the population is not within walking distance of public transport after 7 on any night of the week," says Dr Paul Mees, senior lecturer in transport and land use planning at the University of Melbourne. "Australian cities are not planned to achieve social goals. They are organised so the poorest people … live in the outer suburbs, where public transport is also the poorest."

Sarah Hinde from the National Centre for Epidemiology and Population Health at the Australian National University has been researching the influence of socio-economic status on transport choice. She found that once mothers with children were accounted for (the biggest car users across all groups), people from more privileged backgrounds were less reliant on cars and had more opportunity to walk or take public transport to work.

"This was usually because they could afford to live in the inner suburbs which were close to work and serviced by good public transport," says Hinde.

Unless there are systematic changes to public transport, Mees warns against urging lower income households to change their commuting habits. "Working class people are getting sick of being preached at by wealthy people who've exiled them to the urban fringes."#

The modelling showed that if carbon is priced at $50 a tonne, which is a realistic estimate, then that will cost poor households an extra $1316 a year to carry out the same level of spending. This represents a 4.6 per cent increase in household expenditure. In contrast, the expenditure of high-income households will only increase by 0.7 per cent by paying an extra $2891 a year.

"Low-income households have significantly smaller carbon footprints than high income households, 24 versus 53 tonnes," says Stanley, "but carbon prices will cost poorer people proportionately more."

The increased costs will not only make disadvantaged people worse off; they will also increase the pool of disadvantaged people, says Stanley.

"Fifteen per cent of Australian families are currently disadvantaged, living under the poverty line, (of about $512 a week income for a household of two adults and two children). The next gradient of people who are just managing to stay above the poverty line will be pushed under by the increased costs of living," says Stanley, who is working to estimate how many people this will affect.

In a submission to the Prime Ministerial Task Group on Emissions Trading this year, the brotherhood, the Catholic Social Services Australia and the National Welfare Rights Network argued for a national fund to assist low-income and otherwise disadvantaged people to manage their exposure to the consequences of both climate change itself and policy responses to it.

"We're arguing against issuing free trading permits," says Stanley. "Instead we'd like to see revenue from emission trading scheme permit sales used to create an income pool that would fund schemes to help low-income households insulate their houses, install rainwater tanks and renewable

energy technology, and so reduce their overall energy and living costs."

A small number of programs has already been introduced to assist low-income households become more sustainable. No-interest loans for buying essential white goods and car repairs are one example. The two-year affordable water and energy efficiency program, which was funded until June this year, is another. Jointly run by the NSW Council of Social Service and the NSW Department of Energy, Utilities and Sustainability, its focus has been to improve the energy and water efficiency of low-income households and crisis accommodation providers.